Author name code: johansson ADS astronomy entries on 2022-09-14 author:"Johansson, Sven-Eric" ------------------------------------------------------------------------ Title: VizieR Online Data Catalog: {eta} Car emission spectrum (1700-10400Å) (Zethson+, 2012) Authors: Zethson, T.; Johansson, S.; Hartman, H.; Gull, T. R. Bibcode: 2012yCat..35400133Z Altcode: 2012yCat..35409133Z The spectra were recorded in a low state (March 1998) and an early high state (February 1999) with the Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS) from 1640 to 10400Å using the 52"x0.1" aperture centered on Eta Carinae at position angle, PA=332 degrees. Extractions of the reduced spectrum including both Weigelt B and D, 0.28" in length along the slit, were used to identify the narrow, nebular emission lines, measure their wavelengths and estimate their fluxes.

A linelist of 2500 lines is presented for the high and low states of the combined Weigelt blobs B and D.

(1 data file). Title: η Carinae: linelist for the emission spectrum of the Weigelt blobs in the 1700 to 10 400 Å wavelength region Authors: Zethson, T.; Johansson, S.; Hartman, H.; Gull, T. R. Bibcode: 2012A&A...540A.133Z Altcode:
Aims: We present line identifications in the 1700 to 10 400 Å region for the Weigelt blobs B and D, located 0″.1 to 0″.3 NNW of Eta Carinae. The aim of this work is to characterize the behavior of these luminous, dense gas blobs in response to the broad high-state and the short low-state of η Carinae during its 5.54-year spectroscopic period.
Methods: The spectra were recorded in a low state (March 1998) and an early high state (February 1999) with the Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS) from 1640 to 10 400 Å using the 52″ × 0″.1 aperture centered on Eta Carinae at position angle, PA = 332 degrees. Extractions of the reduced spectrum including both Weigelt B and D, 0″.28 in length along the slit, were used to identify the narrow, nebular emission lines, measure their wavelengths and estimate their fluxes.
Results: A linelist of 2500 lines is presented for the high and low states of the combined Weigelt blobs B and D. The spectra are dominated by emission lines from the iron-group elements, but include lines from lighter elements including parity-permitted and forbidden lines. A number of lines are fluorescent lines pumped by H Lyα. Other lines show anomalous excitation.

Table C.1 is also available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/540/A133 Title: VUV oscillator strengths for iron lines of astrophysical importance Authors: Hartman, H.; Nilsson, H.; Huldt, S.; Johansson, S.; Sörensen, S.; Johnson, M. S.; von Hessberg, P. Bibcode: 2008JPhCS.130a2010H Altcode: FeII lines are of great importance in analyses of stars and nebulae, not only for abundance studies, but also for diagnostics of the plasma conditions and derivation of physical properties such as temperature, electron density and radiation field.

We present a project where the ultimate goal is to derive transition rates for specific Fe II 4s — 5p transitions at VUV wavelengths. These are important for many astrophysical applications, e.g. in objects where line fluorescence is prominent as well as stars observed in the ultraviolet FUSE and HST/STIS region. In this wavelength region many other iron-group element ions have important transitions, which also will be measured. This work is performed as absorption measurements using a FeII hollow-cathode discharge, illuminated by synchrotron radiation at the MAX-lab facility (Lund, Sweden). The intensity ratio between absorption lines from a specific lower level can be determined, and transformed to an absolute scale using previously known f-values for a few lines.

We present results from low spectral resolution test runs on MAX-I, and outline the next step with its requirements for a high-resolution setup at MAX-III. Title: Unidentified lines in the spectra of two iron overabundant CP stars: are they FeII lines? Authors: Castelli, F.; Johansson, S.; Hubrig, S. Bibcode: 2008JPhCS.130a2003C Altcode: The analysis of the high-resolution UVES spectra of the chemically peculiar stars HR6000 and 46 Aql has revealed the presence of an impressive number of unidentified lines, mostly concentrated in the regions 4404-4411 Å and 5100-5300 Å. Almost all of the unidentified lines are the same in both stars, which both have an iron abundance enhancement of the order of +0.7 dex over the solar value. The parameters adopted for HR 6000 and 46 Aql are Teff=12850 K, log g=4.1 and Teff=12750 K, log g=3.8, respectively. We show that some of the unknown lines can be identified as high-excitation (lower EP13eV) FeII and that most of them appear as unclassified lines in laboratory iron spectra. Title: Precision Laboratory UV and IR Wavelengths for Cosmological and Astrophysical Applications Authors: Aldenius, M.; Johansson, S. Bibcode: 2008psa..conf..257A Altcode: 2007astro.ph..3356A The quality of astronomical spectra is now so high that the accuracy of the laboratory data is getting more and more important. Both in astrophysics and in cosmology the needs for accurate laboratory wavelengths have increased with the development of new ground-based and air-borne telescopes and spectrographs. The high-resolution UV Fourier Transform (FT) spectrometer at Lund Observatory is being used for studying laboratory spectra of astrophysically important elements. Title: Possibility of Heterodyne Correlation Interferometry with a Tunable Laser and Absolute Frequency Measurements Authors: Johansson, S.; Letokhov, V. Bibcode: 2008psa..conf..243J Altcode: We consider the possibility of measuring the true width of the narrow optical spectral lines of astrophysical lasers. The lines should have a subDoppler spectral with of 30-100 MHz or even less. To make measurements with spectral resolution better than 107 and angular resolution better than 0.1 arcsec we suggest to use the ground-based Brown-Twiss-Townes optical heterodyne intensity correlation interferometry with the possibility of absolute frequency measurement. The estimates made of the S/N ratio for optical heterodyne astrophysical laser experiments imply that it should be feasible. Title: Astrophysical lasers and nonlinear optical effects in space Authors: Johansson, S.; Letokhov, V. S. Bibcode: 2007NewAR..51..443J Altcode: The present state of the art concerning astrophysical lasers (APL) and nonlinear optical effects under astrophysical conditions is reviewed. The operational conditions of an APL (amplification under non-LTE conditions) and astrophysical predecessors of the laboratory lasers are considered in the introduction of the review. The rareness of observed APL action in the visible range in comparison with astrophysical masers (APM) in the microwave range is explained. Early proposals of APLs with collisional and optical pumping are discussed. APL/M in the mid-IR and submillimeter ranges linking APL and APM are also discussed. APLs in the Weigelt blobs of Eta Carinae operating in FeII and OI with a Bowen type optical pumping are considered in detail. General questions (narrowing of APL spectral lines, the possibility of scattering feedback and ways of measuring the true spectral width of an APL) are considered. Nonlinear optical effects in astrophysical conditions and resonance-enhanced two-photon conditions, in particular, are discussed in the conclusion. Title: Accurate Ritz wavelengths of parity-forbidden [Fe II], [Ti II], and [Cr II] infrared lines of astrophysical interest Authors: Aldenius, M.; Johansson, S. Bibcode: 2007A&A...467..753A Altcode: 2007astro.ph..3145A Context: With new astronomical infrared spectrographs the demands of accurate atomic data in the infrared have increased. In this region there is a large amount of parity-forbidden lines, which are of importance in diagnostics of low-density astrophysical plasmas.
Aims: We present improved, experimentally determined, energy levels for the lowest even LS terms of Fe II, Ti II and Cr II, along with accurate Ritz wavelengths for parity-forbidden transitions between and within these terms.
Methods: Spectra of Fe II, Ti II and Cr II have been produced in a hollow cathode discharge lamp and acquired using high-resolution Fourier Transform (FT) spectrometry. The energy levels have been determined by using observed allowed ultraviolet transitions connecting the even terms with upper odd terms. Ritz wavelengths of parity-forbidden lines have then been determined.
Results: Energy levels of the four lowest Fe II terms (a6D, a4F, a4D and a4P) have been determined, resulting in 97 different parity-forbidden transitions with wavelengths between 0.74 and 87 μm. For Ti II the energy levels of the two lowest terms (a4F and b4F) have been determined, resulting in 24 different parity-forbidden transitions with wavelengths between 8.9 and 130 μm. Also for Cr II the energy levels of the two lowest terms (a6S and a6D) have been determined, in this case resulting in 12 different parity-forbidden transitions with wavelengths between 0.80 and 140 μm.

Tables 6-8 are only available in electronic form at http://www.aanda.org Title: Experimental Mg I oscillator strengths and radiative lifetimes for astrophysical applications on metal-poor stars. New data for the Mg I b triplet Authors: Aldenius, M.; Tanner, J. D.; Johansson, S.; Lundberg, H.; Ryan, S. G. Bibcode: 2007A&A...461..767A Altcode: 2006astro.ph.10033A Context: The stellar abundance ratio of Mg/Fe is an important tool in diagnostics of galaxy evolution. In order to make reliable measurements of the Mg abundance of stars, it is necessary to have accurate values for the oscillator strength (f-value) of each of the observable transitions. In metal-poor stars the Mg I 3p-4s triplet around 5175 Å (Fraunhofer's so-called b lines) are the most prominent magnesium lines. The lines also appear as strong features in the solar spectrum.
Aims: We present new and improved experimental oscillator strengths for the optical Mg I 3p-4s triplet, along with experimental radiative lifetimes for six terms in Mg I. With these data we discuss the implications on previous and future abundance analyses of metal-poor stars.
Methods: The oscillator strengths have been determined by combining radiative lifetimes with branching fractions, where the radiative lifetimes are measured using the laser induced fluorescence technique and the branching fractions are determined using intensity calibrated Fourier Transform (FT) spectra. The FT spectra are also used for determining new accurate laboratory wavelengths for the 3p-4s transitions.
Results: The f-values of the Mg I 3p-4s lines have been determined with an absolute uncertainty of 9%, giving an uncertainty of ± 0.04 dex in the log gf values. Compared to values previously used in abundance analyses of metal-poor stars, rescaling to the new values implies an increase of typically 0.04 dex in the magnesium abundance. Title: New and improved experimental oscillator strengths in Zr II and the solar abundance of zirconium Authors: Ljung, G.; Nilsson, H.; Asplund, M.; Johansson, S. Bibcode: 2006A&A...456.1181L Altcode: Using the Fourier Transform Spectrometer at Lund Observatory, intensity calibrated spectra of singly ionized zirconium have been recorded and analyzed. Oscillator strengths for 263 Zr II spectral lines in the region 2500-5400 Å have been derived by combining new experimental branching fractions with previously measured radiative lifetimes. The transitions combine 34 odd parity levels with 29 low metastable levels between 0 and 2.4 eV. The experimental branching fractions have been compared with theoretical values and the oscillator strengths with previously published data when available. The oscillator strengths have been employed to derive the solar photospheric Zr abundance based on both 1D and 3D model atmospheres. Based on the seven best and least perturbed Zr II lines in the solar disk-center spectrum, we determine the solar Zr abundance to log ɛ_Zr=2.58±0.02 when using a 3D hydrodynamical solar model atmosphere. The new value is in excellent agreement with the meteoritic Zr abundance. Title: Accurate laboratory ultraviolet wavelengths for quasar absorption-line constraints on varying fundamental constants Authors: Aldenius, M.; Johansson, S.; Murphy, M. T. Bibcode: 2006MNRAS.370..444A Altcode: 2006MNRAS.tmp..601A; 2006astro.ph..5053A The most precise method of investigating possible space-time variations of the fine-structure constant, α ≡ (1/ħc)(e2/4πɛ0), using high-redshift quasar absorption lines is the many-multiplet (MM) method. For reliable results this method requires very accurate relative laboratory wavelengths for a number of UV resonance transitions from several different ionic species. For this purpose laboratory wavelengths and wavenumbers of 23 UV lines from MgI, MgII, TiII, CrII, MnII, FeII and ZnII have been measured using high-resolution Fourier transform (FT) spectrometry. The spectra of the different ions (except for one FeII line, one MgI line and the TiII lines) are all measured simultaneously in the same FT spectrometry recording by using a composite hollow cathode as a light source. This decreases the relative uncertainties of all the wavelengths. In addition to any measurement uncertainty, the wavelength uncertainty is determined by that of the ArII calibration lines, by possible pressure shifts and by illumination effects. The absolute wavenumbers have uncertainties of typically +/-0.001-+/-0.002cm-1 (Δ λ ~ 0.06-0.1mÅ at 2500Å), while the relative wavenumbers for strong, symmetric lines in the same spectral recording have uncertainties of +/- 0.0005 cm-1 (Δλ ~ 0.03mÅ at 2500Å) or better, depending mostly on uncertainties in the line-fitting procedure. This high relative precision greatly reduces the potential for systematic effects in the MM method, while the new TiII measurements now allow these transitions to be used in MM analyses. Title: Resonance-enhanced two-photon ionization (RETPI) of Si II and an anomalous, variable intensity of the λ1892 Si III] line in the Weigelt blobs of η Carinae Authors: Johansson, S.; Hartman, H.; Letokhov, V. S. Bibcode: 2006A&A...452..253J Altcode: 2006astro.ph..2365J Context: .The Si III] 1892 Å intercombination line shows an anomalously high intensity in spectra of the radiation-rich Weigelt blobs in the vicinity of Eta Carinae. The line disappears during the 100 days long spectral events occurring every 5.5 years.
Aims: .The aim is to investigate whether resonance-enhanced two-photon ionization (RETPI) is a plausible excitation mechanism for the Si III] λ1892 line.
Methods: .The possible intensity enhancement of the λ1892 line is investigated as regards quasi-resonant intermediate energy levels of Si II.
Results: .The RETPI mechanism is effective on Si II in the radiation-rich Weigelt blobs where the two excitation steps are provided by the two intense hydrogen lines Lyα and Lyγ.
Title: The nature of ultraviolet spectra of AG Pegasi and other symbiotic stars: locations, origins, and excitation mechanisms of emission lines Authors: Eriksson, M.; Johansson, S.; Wahlgren, G. M. Bibcode: 2006A&A...451..157E Altcode: A detailed study of ultraviolet spectra of the symbiotic star AG Peg has been undertaken to derive the atomic excitation mechanisms and origin of formation for the lines common in symbiotic systems. More than 600 emission lines are observed in spectra from {IUE}, {HST} and {FUSE} of which 585 are identified. Population mechanisms and origin of formation are given for a majority of those lines. Based on the understanding of the AG Peg spectra {IUE} data of 19 additional symbiotic stars are investigated and differences and similarities of their spectra are discussed. Fe II fluorescence lines pumped by strong emission lines between 1000 and 2000 Å are observed in 13 of these systems. Some of the symbiotic systems belonging to the subclass symbiotic novae have more than 100 Fe II fluorescence lines in the ultraviolet wavelength region. Forbidden lines are detected for 13 of the stars, mostly from highly-ionized spectra such as Ar V, Ne V and Mg V. Further, [Mg VI] and [Mg VII] lines are observed in a symbiotic star (AG Dra) for the first time. Five of the symbiotic stars have broad white-dwarf wind profiles ({FWHM} > 400 km s-1) for a few lines in their spectra. The stars with no such broad lines can be divided into two similarly sized groups, one where all lines have FWHM less than 70 km s-1 and the other where one, a few or all of the broad ({FWHM} > 400 km s-1) lines of AG Peg have an enhanced broad wing (110-140 km s-1). Title: Astrophysical laser operating in the OI 8446-Åline in the Weigelt blobs of η Carinae Authors: Johansson, S.; Letokhov, V. S. Bibcode: 2005MNRAS.364..731J Altcode: 2005MNRAS.tmp..964J Within the framework of a simple model of photophysical processes in the Weigelt blobs in the vicinity of the luminous blue variable (LBV) star η Carinae, we explain the presence of the fluorescent <OI> 8446-Åand forbidden [OI] 6300-Ålines as well as the absence of the allowed OI 7774-Åline in spectra recorded with the Hubble Space Telescope (HST)/STIS instrument (Gull et al.). From atomic data and estimated stellar parameters we demonstrate that there is a population inversion and stimulated emission in the 3p3P-3s3S transition λ8446 due to photoexcitation by accidental resonance (PAR) by H Lyβ radiation. Title: Bowen excitation of O III and N III in symbiotic stars Authors: Eriksson, M.; Wahlgren, G. M.; Johansson, S. Bibcode: 2005AAS...207.1302E Altcode: 2005BAAS...37.1173E When ions in a plasma are subjected to emission lines very close in photon energy to the energy difference between two levels in the ions, the photons can pump the ions through the corresponding channel. This is called photoexcitation by accidental resonance (PAR). The most famous example of PAR is the Bowen mechanism, where the He II Lyα line at 303.783 Å pumps two 2p2 - 2p3d channels in O III, at 303.800 and 303.695 Å, resulting in the so called O III Bowen lines between 2800 and 4000 Å. In IUE spectra of 20 symbiotic stars we observe the O III Bowen lines in 16. The O III Bowen lines are analyzed and the pumping efficiencies are discussed. In spectra of four of the symbiotic stars, AG Peg, RR Tel, HM Sge and V1016 Cyg, we observethe N III 3s-3p lines at 4000 Å and the 3p-3d lines at 4640 Å are observed. It was proposed already by Bowen (1935) that one of the O III lines, λ 374.432 could photoexcite N III through the channels at 374.434 and 374.442 Å, which would actually lead to the N III lines we observe in the symbiotic stars. We have modeled intensity ratios between the N III lines to test pumping by O III emission as the explanation for the N III 3s-3p and 3p-3d emission. This is valid for AG Peg but can be excluded for HM Sge. For RR Tel and V1016 Cyg the Bowen mechanism seems to be involved in the formation of the N III lines, but additional processes such as radiative recombination or charge-exchange with neutral hydrogen are needed to explain the observed intensity ratios. Title: The FERRUM project: experimentally determined metastable lifetimes and transition probabilities for forbidden [TiII] lines observed in η Carinae Authors: Hartman, H.; Schef, P.; Lundin, P.; Ellmann, A.; Johansson, S.; Lundberg, H.; Mannervik, S.; Norlin, L. -O.; Rostohar, D.; Royen, P. Bibcode: 2005MNRAS.361..206H Altcode: 2005MNRAS.tmp..563H In the spectrum of an emission-line region ejected from the massive star Eta Carinae, called the strontium filament (SrF), forbidden lines from many elements, in particular [SrII] and [TiII], are observed. These lines are strong in this specific region and valuable for plasma diagnostics. Forbidden lines are not easily produced in laboratory light sources and the atomic parameters for these lines can thus not be measured in a straightforward way.

We use a combination of laboratory and astrophysical measurements to determine transition probabilities for the [TiII] lines. Lifetimes for metastable levels in TiII are measured using a laser probing technique on a stored ion beam at CRYRING, MSL, Stockholm. Branching fractions from some of these levels are derived from Hubble Space Telescope/STIS spectra of the SrF. The astrophysical branching fractions are combined with the experimental lifetimes to determine absolute transition probabilities.

We report lifetimes for the TiII levels b4P3/2, b2P1/2, c2D3/2 and c2D5/2, in the range 0.29-17 s, and transition probabilities for eight parity-forbidden lines from the levels c2D3/2 and c2D5/2, along with uncertainty estimates. Title: Time variations of the narrow Fe II and H I spectral emission lines from the close vicinity of η Carinae during the spectral event of 2003 Authors: Hartman, H.; Damineli, A.; Johansson, S.; Letokhov, V. S. Bibcode: 2005A&A...436..945H Altcode: 2005astro.ph..3410H The spectrum of Eta Carinae and its ejecta shows slow variations over a period of 5.5 years. However, the spectrum changes drastically on a time scale of days once every period called the "spectral event". We report on variations in the narrow emission line spectrum of gas condensations (the Weigelt blobs) close to the central star during a spectral event. The rapid changes in the stellar radiation field illuminating the blobs make the blobs a natural astrophysical laboratory to study atomic photoprocesses. The different responses of the HI Paschen lines, fluorescent <Fe II> lines and forbidden [Fe II] lines allow us to identify the processes and estimate physical conditions in the blobs. This paper is based on observations from the Pico dos Dias Observatory (LNA/Brazil) during the previous event in June 2003. Title: Astrophysical Lasers in Optical Fe II Lines in Gas Condensations near η Carinae Authors: Johansson, S.; Letokhov, V. S. Bibcode: 2005AIPC..770..399J Altcode: We report here on the discovery of laser action in the range 0.9-2 μm in several spectral lines of Fe II, which are associated with transitions from ``pseudo-metastable'' states populated by spontaneous transitions from Lyα pumped Fe II levels. The intense Lyα radiation is formed in the HII region of gas condensations close to the star η Car. The laser transitions form together with spontaneous transitions closed radiative cycles, one of which includes the extremely bright 2507/09 Å lines. This fact, together with an accidental mixing of energy levels, may provide an explanation of the abnormal intensities of these UV non-lasing lines. Using the complicated energy level diagram of Fe II we present those peculiar features, which are essential for the inverted population and laser effect: the pumping, the level mixing, and the ``bottle neck'' for spontaneous decay. The laser action is a new indicator of non-equilibrium and spatially non-homogeneous physical conditions as well as a high brightness temperature of Lyα in ejecta from eruptive stars. Such conditions are very difficult to probe by existing methods. Title: Metastable hydrogen absorption in ejecta close to η Carinae Authors: Johansson, S.; Gull, T. R.; Hartman, H.; Letokhov, V. S. Bibcode: 2005A&A...435..183J Altcode: Spectroscopy with the high spatial resolution of the Hubble Space Telescope (HST) reveals narrow absorption in the hydrogen Balmer lines in spectra of Eta Carinae and the nearby nebular-scattered starlight. While hydrogen Balmer absorption lines are seen in stellar photospheres and winds, we are not aware of such being seen in galactic nebulae. This exceptional case is caused by intense stellar UV radiation acting on high-density neutral clumps of gas in the close vicinity of the central source. The interaction of the UV radiation with hydrogen results in photo-ionization and photo-excitation leading to a non-equilibrium population of the metastable 2s 2S level. This occurs throughout the equatorial region surrounding η Carinae in sufficient quantity to produce strong narrow absorption on top of the broad P Cygni emission profile. This absorption can be considered to be a probe of the very non-uniform ejecta in the disk region surrounding η Carinae. Title: Bowen excitation of N III lines in symbiotic stars Authors: Eriksson, M.; Johansson, S.; Wahlgren, G. M.; Veenhuizen, H.; Munari, U.; Siviero, A. Bibcode: 2005A&A...434..397E Altcode: We present a semi-empirical equation for prediction of the strengths of those N III lines that are generated by the Bowen mechanism and observed in spectra of symbiotic stars. The equation assumes that the Bowen mechanism is the only source populating the 3d state in N III, and comparisons with observations of the 3s-3p and 3p-3d transitions serve as a test of this assumption. In an ongoing study of symbiotic stars the equation has been applied to two symbiotic novae, RR Tel and AG Peg, by comparing the predicted N III line strengths to observed line intensities. It is clear that besides the Bowen mechanism there is another process, most likely radiative recombination, that contributes to the N III 3d population in AG Peg and is the main population process of this state in RR Tel. It is also clear that a second, not previously considered, N III channel, 2p 2P{1/2}-3d 2D{3/2} at 374.198 Å, is pumped by O III in both RR Tel and AG Peg. Title: Possibility of measuring the width of narrow Fe II astrophysical laser lines in the vicinity of η Carinae by means of Brown-Twiss-Townes heterodyne correlation interferometry Authors: Johansson, S.; Letokhov, V. S. Bibcode: 2005NewA...10..361J Altcode: 2005astro.ph..1246J We consider the possibility of measuring the true width of the narrow Fe II optical lines observed in spectra of the Weigelt blobs in the vicinity of η Carinae. The lines originate as a result of stimulated amplification of spontaneous emission of radiation in quantum transitions between energy levels showing inverted population [Johansson, S., Letokhov, V., 2002. JETP Lett. 75 (10) 495; Johansson, S., Letokhov, V., 2003. Phys. Rev. Lett. 90 (1) 01110-1; Johansson, S., Letokhov, V., 2004. A&A 428,497]. The lines should have a subDoppler spectral width of 30-100 MHz, depending on the geometry of the lasing volume. To make measurements with a spectral resolution of R > 107 and an angular resolution better than 0.1″, we suggest the use of the Brown-Twiss-Townes optical heterodyne intensity correlation interferometry. The estimates made of the S/N ratio for the optical heterodyne astrophysical laser experiment imply that it is feasible. Title: Experimental Oscillator Strengths for Forbidden Lines in Complex Spectra Authors: Hartman, H.; Johansson, S.; Lundberg, H.; Lundin, P.; Mannervik, S.; Schef, P. Bibcode: 2005PhST..119...40H Altcode: In dilute astrophysical plasmas, such as planetary nebulae and H II regions, strong lines appear that only have weak, if any, correspondence to the spectrum of laboratory light sources. Some of these are parity forbidden lines, i.e. emission from long-lived metastable states that cannot decay via normal electric dipole (E1) routes but only via the slower M1 and E2 transitions. The long lifetime of the upper levels and their sensitivity to collisions make the lines good diagnostics of the emitting plasma, but then the transition probability, or A-value, of these lines must be known.

We report on a technique to experimentally determine A-values for forbidden lines using the method of combining the lifetime of the upper level with the branching fractions for the different decay channels. The lifetime is measured using the laser probing technique (LPT) on a stored ion beam. Since these lines are rarely produced in laboratory plasmas, we use astrophysical spectra to determine the branching fractions (BF). The lifetime and the BF then give the A-value, which is one quantity needed for modeling the spectrum of the plasma emitting the forbidden lines.

The present measurements are performed within the FERRUM project, an international collaboration producing and evaluating transition probabilities for iron group element lines of astrophysical importance (Johansson P I S et al 2002 Physica Scripta T100 71) Title: Stimulated Amplification under Spatially Nonhomogeneous Conditions: An Astrophysical Fe II Laser in the Vicinity of Eta Carinae Authors: Johansson, S.; Letokhov, V. Bibcode: 2005PhST..120...99J Altcode: We consider the conditions necessary for the development of an inverted population among the energy levels of free atoms in a medium exposed to radiation in spectral non-equilibrium. In particular, we focus on monochromatic radiation occurring as a result of an accidental wavelength coincidence between a pumping emission line and a pumped absorption line in two different elements. We examine especially the influence of `pseudo-metastable' states (at medium excitation) in the complex spectrum of Fe II, which cause a `bottleneck' in the radiative decay leading to an inverted level population. We also discuss the effect of `spectral compression' of the Lyman continuum into HLyα radiation at a high effective temperature. In conclusion we describe those differences between microwave astrophysical masers (APM) and optical astrophysical lasers (APL) that make the latter a more rare phenomenon in Nature. Title: Astrophysical lasers operating in optical Fe II lines in stellar ejecta of η Carinae Authors: Johansson, S.; Letokhov, V. S. Bibcode: 2004A&A...428..497J Altcode: 2004astro.ph..9069J After the discovery of space masers based on OH radicals (Weaver et al. \cite{Wea65}) and H2O (Cheung et al. \cite{Che69}) such microwave lasers have been found to work in more than 100 molecular species (Elitzur \cite{Eli92}; Townes \cite{Tow97}), as well as in highly excited H atoms (Strelnitski et al. \cite{Str96}). In the IR region (10 \mum), the effect of stimulated emission of radiation in the CO2 molecule has been discovered in the Martian and Venus' atmospheres (Betz et al. \cite{Bet76}; Mumma et al. \cite{Mum81}). We report here on the discovery of laser action in the range 0.9-2 μm in several spectral lines of Fe II, which are associated with transitions from ``pseudo-metastable'' states populated by spontaneous transitions from Lyα pumped Fe II levels. The intense Lyα radiation is formed in the HII region of gas condensations close to the star η Car. The laser transitions form together with spontaneous transitions closed radiative cycles, one of which includes the extremely bright 2507/09 Å lines. Closed radiative cycles, together with an accidental mixing of energy levels, may provide an explanation of the abnormal intensities of these UV non-lasing lines. Using the complicated energy level diagram of Fe II we present those peculiar features, which are essential for the inverted population and laser effect: the pumping, the level mixing, and the ``bottle neck'' for spontaneous decay. The laser action is a new indicator of non-equilibrium and spatially non-homogeneous physical conditions as well as a high brightness temperature of Lyα in ejecta from eruptive stars. Such conditions are very difficult to probe by existing methods, and we propose some future experiments. The fact, that the lasing near-IR lines appear in the spectrum with about the same intensity as non-lasing lines is discussed and compared with the situation in masers. Title: Fe II Diagnostic Tools for Quasars Authors: Verner, E.; Bruhweiler, F.; Verner, D.; Johansson, S.; Kallman, T.; Gull, T. Bibcode: 2004ApJ...611..780V Altcode: 2004astro.ph..4593V The enrichment of Fe relative to α-elements such as O and Mg represents a potential means to determine the age of quasars and probe the galaxy formation epoch. To explore how Fe II emission in quasars is linked to physical conditions and abundance, we have constructed an 830 level Fe II model atom and investigated through photoionization calculations how Fe II emission strengths depend on nonabundance factors. We have split Fe II emission into three major wavelength bands, Fe II (UV), Fe II (Opt1), and Fe II (Opt2), and explore how the Fe II (UV)/Mg II, Fe II (UV)/Fe II (Opt1), and Fe II (UV)/Fe II (Opt2) emission ratios depend on hydrogen density and ionizing flux in the broad-line regions (BLRs) of quasars. Our calculations show that (1) similar Fe II (UV)/Mg II ratios can exist over a wide range of physical conditions, (2) the Fe II (UV)/Fe II (Opt1) and Fe II (UV)/Fe II (Opt2) ratios serve to constrain ionizing luminosity and hydrogen density, and (3) flux measurements of Fe II bands and knowledge of the ionizing flux provide tools to derive distances to BLRs in quasars. To derive all BLR physical parameters with uncertainties, comparisons of our model with observations of a large quasar sample at low redshift (z<1) are desirable. The STIS and NICMOS instruments aboard the Hubble Space Telescope offer the best means to provide such observations. Title: Fe II fluorescence in symbiotic stars Authors: Eriksson, M.; Veenhuizen, H.; Wahlgren, G. M.; Johansson, S. Bibcode: 2004RMxAC..21..132E Altcode: 2004IAUCo.191..132E Fe 0 fluorescence by PAR has been investigated in eight symbiotic stars having a wide range in temperature of the hot component and orbital period. The data used are spectra obtained from the IUE archive. All pumping lines investigated in this work are in the short wavelength region of IUE (1200-2000 Å), except for He 0 λ 1084.942 and O 0 λ 1032.041. The resulting Fe 0 fluorescence lines are mainly in the long wavelength region (2000-3300 Å), but a few fall in the same region as the pumping lines. The aim is to understand the optimal conditions for formation of Fe 0 fluorescence lines caused by PAR. Three of the selected systems, RR Tel, AG Peg and V1016 Cyg, have 10-30 active Fe 0 channels. Two conditions connect those systems to each other: The hot component is a white dwarf of extreme temperature (80 . 103-150 . 103 K) and all three systems are so called symbiotic novae and have had outbursts during the last 150 years. Three systems, AG Dra, RW Hya and R Aqr, have only 2-3 active Fe 0 channels. In the two remaining systems, CI Cyg and T CrB, Fe 0 fluorescence lines were totally absent. These two systems have two features in common: The emission strength of highly ionized elements is less than in most symbiotic systems, and the hot component is suspected to be an accreting main sequence star rather than a white dwarf. Title: Modeling the wind structure of AG Peg by fitting of C IV and N V resonance doublets Authors: Eriksson, M.; Johansson, S.; Wahlgren, G. M. Bibcode: 2004A&A...422..987E Altcode: The latest outburst of AG Peg has lasted for 150 years, which makes it the slowest nova eruption ever recorded. During the time of IUE observations (1978-1995) line profiles and intensity ratios of the N V and C IV doublet components changed remarkably, and we discuss plausible reasons. One of them is radiative pumping of Fe II which is investigated by studying the fluorescence lines from pumped levels. Three Fe II channels are pumped by C IV and one by N V. The pumping rates of those Fe II channels as derived by the modeling agree well with the strengths of the Fe II fluorescence lines seen in the spectra. We model the C IV and N V resonance doublets in IUE spectra recorded between 1978 and 1995 in order to derive optical depths, expansion velocities, and the emissivities of the red giant wind, the white dwarf wind and their collision region. The derived expansion velocities are ∼60 km s-1 for the red giant wind and ∼700 km s-1 for the white dwarf wind. We also suggest a fast outflow from the system at ∼150 km s-1. The expansion velocity is slightly higher for N V than for C IV. Emission from the collision region strongly affects the profile of the N V and C IV resonance doublets indicating its existence. Title: Erratum: "Anomalous Fe II Spectral Effects and High H I Lyα Temperature in Gas Blobs Near η Carinae" [Astron. Lett. 30, 58 (2004)] Authors: Johansson, S.; Letokhov, V. S. Bibcode: 2004AstL...30..433J Altcode: No abstract at ADS Title: The Possibility of Resonance-Enhanced Two-Photon Ionization of Ne and Ar Atoms in Astrophysical Plasmas Authors: Johansson, S.; Letokhov, V. S. Bibcode: 2004ARep...48..399J Altcode: We consider possible schemes for the resonance-enhanced two-photon ionization (RETPI) of Ne and Ar atoms under the action of bichromatic radiation of intense resonance lines of HI, HeI, and HeII in a radiation-rich astrophysical plasma. The ionization rate is comparable to or exceeds the recombination rate in rarified astrophysical plasma, which leads to the accumulation of singly ionized ions with a subsequent transition to the higher ionization state via RETPI. We consider the RETPI reaction chains NeI → ... → NeV and ArI → ... → ArVI. Title: Identification of emission lines in the low-ionization strontium filament near Eta Carinae Authors: Hartman, H.; Gull, T.; Johansson, S.; Smith, N.; HST Eta Carinae Treasury Project Team Bibcode: 2004A&A...419..215H Altcode: 2004astro.ph..2489H We have obtained deep spectra from 1640 to 10 100 Å with the Space Telescope Imaging Spectrograph (STIS) of the strontium filament, a largely neutral emission nebulosity lying close to the very luminous star Eta Carinae and showing an uncommon spectrum. Over 600 emission lines, both permitted and forbidden, have been identified. The majority originates from neutral or singly-ionized iron group elements (Sc, Ti, V, Cr, Mn, Fe, Co, Ni). Sr is the only neutron capture element detected. The presence of Sr II, numerous strong Ti II and V II lines and the dominance of Fe I over Fe II are notable discoveries. While emission lines of hydrogen, helium, and nitrogen are associable with other spatial structures at other velocities within the Homunculus, no emission lines from these elements correspond to the spatial structure or velocity of the \ion{Sr} filament. Moreover, no identified \ion{Sr} filament emission line requires an ionization or excitation energy above approximately 8 eV. Ionized gas extends spatially along the aperture, oriented along the polar axis of the Homunculus, and in velocity around the strontium filament. We suggest that the strontium filament is shielded from ultraviolet radiation at energies above 8 eV, but is intensely irradiated by the central star at wavelengths longward of 1500 Å.

Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

Tables 2 and 3 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/419/215 Title: VizieR Online Data Catalog: Emission lines of Sr filament near {eta} Car (Hartman+, 2004) Authors: Hartman, H.; Gull, T.; Johansson, S.; Smith, N.; HST Eta Carinae Treasury Project Team Bibcode: 2004yCat..34190215H Altcode: Spectral lines observed in the Sr-filament of {eta} Car in the wavelength region 2480-10140Å. The lines are sorted by wavelength in table 2 and sorted according to the periodic table in table 3. Both tables are available in postscript format as the file tables23.ps where the sub and superscripts for the atomic transitions are kept.

(3 data files). Title: Anomalous Fe II Spectral Effects and High H I Lyα Temperature in Gas Blobs Near η Carinae Authors: Johansson, S.; Letokhov, V. S. Bibcode: 2004AstL...30...58J Altcode: We consider the origin of the anomalously high intensity of the ultraviolet Fe II lambda 2507/2509 A lines observed with high spatial and spectral resolutions from gas blobs (GBs) near Carinae. This rare effect in stellar spectra is attributable to a combination of several factors: (1) the high hydrogen density (>10^{8} cm^{-3}) that ensures the blocking of the Lyman continuum by GBs and, accordingly, the formation of a cold H I region with completely ionized Fe atoms; (2) the small distance between the GBs and the central star that ensures a high (>8000-10 000 K) Ly_alpha H spectral temperature, which photoexcites Fe II selectively; and (3) the population of Fe II levels and, accordingly, the opening of a stimulated emission channel, which together with spontaneous transitions creates a radiative cycle where a single Fe II ion can multiply absorb Ly_alpha emission. Title: Anomalously bright UV lines of Fe II as a probe of gas condensations in the vicinity of hot stars Authors: Johansson, S.; Letokhov, V. S. Bibcode: 2003A&A...412..771J Altcode: Two UV lines of Fe II at 2507/2509 Å are extremely bright in spatially resolved HST/STIS spectra of dense gas condensations (the so called Weigelt blobs) close to the central star of η Carinae. The lines also appear unresolved in HST/FOS spectra of the star AE And. Under normal conditions the lines should hardly be observable. Based on recent studies of the formation of the łambdałambda2507/2509 lines as part of a radiative cycle driven by HLyα pumping and including stimulated emission we propose the possibility of using them as a probe of non-homogeneities in gas condensations located outside hot, massive stars. Title: Line absorption in the FUSE spectrum of the CP star 17 Com A Authors: Wahlgren, G. M.; Ivarsson, S.; Johansson, S.; Proffitt, C. R.; Adelman, S. J.; Rice, J.; Gulliver, A. F.; Hill, G.; Leckrone, D. S.; Smith, D. P. Bibcode: 2003AAS...203.9303W Altcode: 2003BAAS...35.1358W We report on progress made in our Far Ultraviolet Spectroscopic Explorer (FUSE) program (ID A130; PI J.Rice) that pertains to understanding the absorption line spectrum of the magnetic chemically peculiar B star 17 Com A (HD108662). Spectral observations were made on ten occasions with the FUSE observatory over a five day interval in April 2001 for the purpose of studying temporal flux variations over the stellar rotational period of 5.07 days. These data will allow us to correlate the far-UV flux variations with elemental abundance variations over the stellar surface as mapped out by optical Doppler image mapping techniques. Complementing the FUSE data are high-resolution optical spectra obtained at the Nordic Optical Telescope and the McDonald Observatory. From the optical spectra we have determined the rotational velocity (v sin i = 17 km s-1) and chemical abundances. The iron-group elements are generally enriched by a factor of 10 relative to the solar values and as such, are responsible for a large part of the line absorption in the FUSE spectral region. Using synthetic spectrum techniques with the abundances derived from the optical region data and FUSE archival spectra of normal and non-magnetic CP stars, we can identify approximately two-thirds of the absorption features in the FUSE spectrum of 17 Com A. In particular, we have concentrated on contributions from the Cr II/III and Fe II/III spectra. Aspects of atomic spectroscopy are also being carried out with the FUSE spectra. New experimental oscillator strengths for 4d-4f transitions of Fe II observed at optical wavelengths are used in conjunction with the FUSE spectra of chemically normal B type stars to determine oscillator strengths for important Fe II 3d-4f transitions. Title: Astrophysical Lasers with Radiation Pumping by Accidental Resonance Authors: Johansson, S.; Letokhov, V. S. Bibcode: 2003PASP..115.1375J Altcode: In this paper we consider a general problem of astrophysical lasers operating with optical pumping by accidental resonance (PAR) with strong spontaneous emission lines of other elements. The origin of population inversion and the coefficient of amplification due to the optical excitation of atoms (ions) by a four-level scheme with PAR are analyzed. We elucidate conclusively the question of the manifestation of astrophysical lasers in the optical region of the spectrum, which in principle differs from that of astrophysical masers in the microwave range. Title: The HST Treasury Project on Eta Carinae Authors: Davidson, K.; Ishibashi, K.; Gull, T. R.; Martin, J. C.; Humphreys, R. M.; Damineli, A.; Weis, K.; Stahl, O.; Hillier, D. J.; Corcoran, M.; Hamann, F.; Walborn, N.; Johansson, S.; Hartman, H.; Bautista, M. Bibcode: 2003AAS...203.5805D Altcode: 2003BAAS...35.1302D This program is valuable for a broad range of stellar and nebular astrophysics, as well as data processing techniques and instrument characteristics. While observing this object's mysterious 5.5-year cycle, we obtained data on several distinct, complex, unfamiliar classes of spectra which cannot be observed well elsewhere. The stellar wind parameters lie outside normal experience, the Weigelt ejecta produce narrow-line spectra unlike any other known object, and the other spectra are also unusual. Altogether our results pertain to stellar instabilities close to the Eddington limit, extreme stellar winds, unexplored nebular/atomic excitation processes, nebular gas dynamics, and instrument performance.

The project also represents an extreme application of HST spectroscopy. Since η Car and its ejecta are spatially, spectrally, and temporally complex, they require the best available performance of HST/STIS across its full wavelength range. Such observations will probably not be attainable again within the next 15 years. They also require improved data processing techniques which we have developed, useful for HST/STIS programs on other objects. The Eta Car Treasury data archive will be pertinent to a variety of significant problems mentioned above -- not just η Carinae. (See a related poster concerning the Archive.)

Here we report that (1) the predicted event did indeed occur during May--July 2003; (2) we obtained the planned data; (3) they show numerous fascinating and difficult-to-explain phenomena; and (4) we sketch improved reduction routines to achieve maximum resolution with STIS/CCD data in general. We also show examples of the spectral structure and variations in Eta Carinae.

This project is supported by STScI grant GO-9420. Title: Improved oscillator strengths and wavelengths for Os I and Ir I, and new results on early r-process nucleosynthesis Authors: Ivarsson, S.; Andersen, J.; Nordström, B.; Dai, X.; Johansson, S.; Lundberg, H.; Nilsson, H.; Hill, V.; Lundqvist, M.; Wyart, J. F. Bibcode: 2003A&A...409.1141I Altcode: The radioactive decay of 238U and 232Th has recently been used to determine ages for some of the oldest stars in the Universe. This has highlighted the need for accurate observational constraints on production models for the heaviest r-process elements which might serve as stable references, notably osmium and iridium. In order to provide a firmer basis for the observed abundances, we have performed laser-induced fluorescence measurements and Fourier Transform Spectroscopy to determine new radiative lifetimes and branching fractions for selected levels in Os I and Ir I. From these data, we determine new absolute oscillator strengths and improved wavelengths for 18 Os I and 4 Ir I lines. A reanalysis of VLT spectra of CS 31082-001 and new results for other stars with Os and Ir detections show that (i): the lines in the UV and lambda 4260 Å yield reliable Os abundances, while those at lambda lambda 4135, 4420 Å are heavily affected by blending; (ii): the Os and Ir abundances are identical in all the stars; (iii): the heavy-element abundances in very metal-poor stars conform closely to the scaled solar r-process pattern throughout the range 56 <= Z <= 77; and (iv): neither Os or Ir nor any lighter species are suitable as reference elements for the radioactive decay of Th and U.

Based in part on observations obtained with the Very Large Telescope of the European Southern Observatory at Paranal, Chile. Title: Revisited Abundance Diagnostics in Quasars: Fe II/Mg II Ratios Authors: Verner, E.; Bruhweiler, F.; Verner, D.; Johansson, S.; Gull, T. Bibcode: 2003ApJ...592L..59V Altcode: 2003astro.ph..6533V Both the Fe II UV emission in the 2000-3000 Å region [Fe II(UV)] and resonance emission line complex of Mg II at 2800 Å are prominent features in quasar spectra. The observed Fe II(UV)/Mg II emission ratios have been proposed as means to measure the buildup of the Fe abundance relative to that of the α-elements C, N, O, Ne, and Mg as a function of redshift. The current observed ratios show large scatter and no obvious dependence on redshift. Thus, it remains unresolved whether a dependence on redshift exists and whether the observed Fe II(UV)/Mg II ratios represent a real nucleosynthesis diagnostic. We have used our new 830 level model atom for Fe+ in photoionization calculations, reproducing the physical conditions in the broad-line regions of quasars. This modeling reveals that interpretations of high values of Fe II(UV)/Mg II are sensitive not only to Fe and Mg abundance, but also to other factors such as microturbulence, density, and properties of the radiation field. We find that the Fe II(UV)/Mg II ratio combined with Fe II(UV)/Fe II(optical) emission ratio, where Fe II(optical) denotes Fe II emission in 4000-6000 Å band, can be used as a reliable nucleosynthesis diagnostic for the Fe/Mg abundance ratios for the physical conditions relevant to the broad-line regions of quasars. This has extreme importance for quasar observations with the Hubble Space Telescope and also with the future James Webb Space Telescope. Title: Experimental f-Value and Isotopic Structure for the Ni I Line Blended with [O I] at 6300 Å Authors: Johansson, S.; Litzén, U.; Lundberg, H.; Zhang, Z. Bibcode: 2003ApJ...584L.107J Altcode: 2003astro.ph..1382J We have measured the oscillator strength of the Ni I line at 6300.34 Å, which is known to be blended with the forbidden line [O I] λ6300 used for the determination of the oxygen abundance in cool stars. We also give wavelengths of the two isotopic line components of 58Ni and 60Ni derived from the asymmetric laboratory line profile. These two line components of Ni I have to be considered when calculating a line profile of the 6300 Å feature observed in stellar and solar spectra. We also discuss the labeling of the energy levels involved in the Ni I line since level mixing makes the theoretical predictions uncertain. Title: The FERRUM Project: Experimental transition probabilities of [Fe II] and astrophysical applications Authors: Hartman, H.; Derkatch, A.; Donnelly, M. P.; Gull, T.; Hibbert, A.; Johansson, S.; Lundberg, H.; Mannervik, S.; Norlin, L. -O.; Rostohar, D.; Royen, P.; Schef, P. Bibcode: 2003A&A...397.1143H Altcode: We report on experimental transition probabilities for thirteen forbidden [Fe II] lines originating from three different metastable Fe Ii levels. Radiative lifetimes have been measured of two metastable states by applying a laser probing technique on a stored ion beam. Branching ratios for the radiative decay channels, i.e. M1 and E2 transitions, are derived from observed intensity ratios of forbidden lines in astrophysical spectra and compared with theoretical data. The lifetimes and branching ratios are combined to derive absolute transition probabilities, A-values.

We present the first experimental lifetime values for the two Fe II levels a4G9/2 and b2H11/2 and A-values for 13 forbidden transitions from a6S5/2, a4G9/2 and b4D7/2 in the optical region. A discrepancy between the measured and calculated values of the lifetime for the b2H11/2 level is discussed in terms of level mixing.\ We have used the code CIV3 to calculate transition probabilities of the a6D-a6S transitions.

We have also studied observational branching ratios for lines from 5 other metastable Fe II levels and compared them to calculated values. A consistency in the deviation between calibrated observational intensity ratios and theoretical branching ratios for lines in a wider wavelength region supports the use of [Fe II] lines for determination of reddening. Title: Temporal Variations of Fe II Fluorescence Lines in the Symbiotic Star AG Peg Authors: Eriksson, M.; Johansson, S.; Wahlgren, G. M. Bibcode: 2003ASPC..303..109E Altcode: 2003ssps.conf..109E No abstract at ADS Title: Radiative Cycle with Stimulated Emission from Atoms and Ions in an Astrophysical Plasma Authors: Johansson, S.; Letokhov, V. S. Bibcode: 2003PhRvL..90a1101J Altcode: 2002astro.ph.12382J We propose that a radiative cycle operates in atoms and ions located in a rarefied gas in the vicinity of a hot star. Besides spontaneous transitions the cycle includes a stimulated transition in one very weak intermediate channel. This radiative “bottleneck” creates a population inversion, which for an appropriate column density results in amplification and stimulated radiation in the weak transition. The stimulated emission opens a fast decay channel leading to a fast radiative cycle in the atom (or ion). We apply this model by explaining two unusually bright FeII lines at 250.7 and 250.9nm in the UV spectrum of gas blobs close to η Carinae, one of the most massive and luminous stars in the Galaxy. Title: Comments on atomic data for the GAIA spectral region Authors: Wahlgren, G. M.; Johansson, S. Bibcode: 2003ASPC..298..481W Altcode: 2003gsst.conf..481W No abstract at ADS Title: The -145 km/s Absorption System of Eta Carinae Authors: Vieira, G. L.; Gull, T. R.; Danks, A. C.; Johansson, S. Bibcode: 2002AAS...201.4904V Altcode: 2002BAAS...34.1184V With the STIS E230H mode (R 118,000), we have identified about twenty absorption components in line of sight from Eta Carinae. Two components, one at -513 km/s and another at -145 km/s, are quite different in character from the others, mostly at intermediate velocities (See adjacent posters by T. Gull and A. Danks). The -145 km/s component is significantly wider in fwhm, is seen in many more species, and the lower level can be above 20,000 cm-1, well above the 2000 cm-1 noted in the -513 km/s component. In the spectral region from 2400 to 3160A, approximately 500 absorption lines have been identified. In this poster, we will present line identifications and atomic parameters of the measured lines, hopefully providing insight as to what levels are being excited and by what processes. Observations were accomplished through STScI under proposal 9242 (Danks, P.I.). Funding is through the STIS GTO resources. Title: Properties of the -513 km/s Ejecta in the Spectrum of Eta Carinae Authors: Danks, A. C.; Gull, T. R.; Vieira, G. L.; Johansson, S. Bibcode: 2002AAS...201.4905D Altcode: 2002BAAS...34.1184D In the spectral region 2400-3160A of Eta Carinae, we have identified approximately 500 absorption lines each with up to twenty velocity components.The -512 km/s component is truely unique as 1) the typical line width is <3 km/s, 2) the identified lines are in Fe I, Fe II, V II and Ti II, and 3) the lines originate from lower levels up to 2000 cm-1 above the ground level. We have measured the velocity centers, full width at half maximum and equivalent widths for approximately 100 absorption lines. Initial results were very confusing as we found more variation in central velocities than would be expected from known STIS echelle wavelength standards. Upon further review, we found that the reporteded wavelengths in the NIST and Kurucz databases were not sufficiently accurate. S. Johansson searched FTS laboratory measurements performed at Lund for V II and Ti II and provided much improved wavelength measures. Likewise, we find more variation in column density than expected statistically from the accuracy of the equivalent widths for lines originating from the same energy level. We are reviewing the published gf values and our measurements to improve the measured column densities. Some spectroscopy of the ejecta has already been accomplished at two different epochs. Preliminary measures of equivalent widths indicate there may be some variation with time, but we await measurements planned for July 2003 during the upcoming spectroscopic minimum of Eta Carinae. These observations were accomplished through STScI and funding was from STIS GTO resources. Title: The FERRUM Project: Experimental oscillator strengths of the UV 8 multiplet and other UV transitions from the y6P levels of Fe II Authors: Pickering, J. C.; Donnelly, M. P.; Nilsson, H.; Hibbert, A.; Johansson, S. Bibcode: 2002A&A...396..715P Altcode: We report on experimental branching fractions (BFs) for 19 transitions from the three 3d5(6S)4s4p(3P) y6P levels in Fe II, measured in Fourier transform spectra of a Penning discharge lamp and a hollow cathode lamp. The transition wavelengths span the interval between 1600 and 2850 Å. Absolute oscillator strengths (f-values) have been derived by combining the BFs with experimental radiative lifetimes recently reported in the literature. Theoretical f-values have been calculated using configuration interaction wavefunctions. The new experimental and theoretical f-values are compared with data available in the literature and in databases. The strongest lines measured belong to the UV 8 multiplet of Fe II, which has one ground state transition appearing as a prominent feature at 1608 Å in interstellar spectra. The line is accompanied by a satellite at 1611 Å due to a level mixing, which is discussed in the paper. Title: The Origin of Fe II and [Fe II] Emission Lines in the 4000-10000 Å Range in the BD Weigelt Blobs of η Carinae Authors: Verner, E. M.; Gull, T. R.; Bruhweiler, F.; Johansson, S.; Ishibashi, K.; Davidson, K. Bibcode: 2002ApJ...581.1154V Altcode: We present numerical simulations that reproduce the salient features of the amazingly strong [Fe II] and Fe II emission spectra in the B and D Weigelt blobs of η Carinae. For our studies we have used spectra obtained during the 1998 epoch observations with the Hubble Space Telescope (HST). The spectrum of the B and D Weigelt blobs dominates in [Fe II] and Fe II emission lines. The same observations show no Fe I or Fe III. We have compared our measurements of the strongest (>=200) [Fe II] and Fe II lines and blends in the spectrum with theoretical predictions. Our predictions are based on non-LTE modeling of the Fe II atom, which includes the lowest 371 energy levels (all levels up to 11.6 eV). We have investigated the dependence of the spectrum on electron density, pumping by the blackbody-like stellar continuum, and intense Lyα emission. We find that radiative pumping is essential in explaining the observed spectrum. We have identified the main pumping routes responsible for the observed Fe II emission. Comparison between the model and observations reveals details of the radiation field. Pumping by the blackbody-like stellar radiation field from η Carinae explains the numerous strong [Fe II] and Fe II lines in the range of 4000-6500 Å. The strongest Fe II lines in a range of 8000-10000 Å are pumped by intense Lyα radiation. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. Title: Erratum: Successsive resonance-enhanced two-photon ionization of elements abundant in nebulae. I. Atoms and ions of C, N, and O Authors: Johansson, S.; Letokhov, V. S. Bibcode: 2002A&A...395..345J Altcode: No abstract at ADS Title: The origin of the anomalous intensity ratio between very bright UV FeII lines and their satellites in gaseous condensations close to the star eta Carinae Authors: Klimov, V.; Johansson, S.; Letokhov, V. S. Bibcode: 2002A&A...385..313K Altcode: We present a model that explains the anomalous intensity ratios between each of two very bright UV lines of Fe II at 2507 Å and 2509 Å and its corresponding satellite line, observed in HST spectra of a compact gaseous condensation (blob B) in the vicinity of the star protect eta Car.The model is based on the assumption that the FeII transitions have a substantial optical thickness, which varies as a result of the photodepletion of the long-lived lower states, c4F7/2,9/2, by the intense Lyalpha radiation. In conditions where the photodepletion rates of these two states differ, the resonance scattering lengths of the spectral lines become different as well. In the presence of a weak, nonresonant (continuous) absorption, this gives rise to a difference in attenuation between the spectral lines (the Hummer effect (Hummer 1968)). It is the combination of these two effects that explains the anomalous (as compared with laboratory data) intensity ratios observed in the two pairs of UV FeII lines. Ionization channels of stimulated photodepletion by the Lyalpha radiation, including the possible role of autoionization levels, are considered. Title: Experimental oscillator strengths in U II of cosmological interest Authors: Nilsson, H.; Ivarsson, S.; Johansson, S.; Lundberg, H. Bibcode: 2002A&A...381.1090N Altcode: Oscillator strengths for 57 U II lines in the region 3500-6700 Å have been derived by combining new branching fraction measurements with recently measured lifetimes. The lines combine six upper levels with numerous low levels having excitation energies of 0-1.5 eV. The data include the U II line at 3859 Å, which is used for cosmochronology. Title: The FERRUM Project: New f-value Data for Fe II and Astrophysical Applications Authors: Johansson, S.; Derkatch, A.; Donnelly, M. P.; Hartman, H.; Hibbert, A.; Karlsson, H.; Kock, M.; Li, Z. S.; Leckrone, D. S.; Litzén, U.; Lundberg, H.; Mannervik, S.; Norlin, L. -O.; Nilsson, H.; Pickering, J.; Raassen, T.; Rostohar, D.; Royen, P.; Schmitt, A.; Johanning, M.; Sikström, C. M.; Smith, P. L.; Svanberg, S.; Wahlgren, G. M. Bibcode: 2002PhST..100...71J Altcode: We present the FERRUM Project, an international collaboration aiming at a production and evaluation of oscillator strengths (transition probabilities) of selected spectral lines of singly ionized iron group elements, that are of astrophysical relevance. The results obtained include measurements and calculations of permitted and forbidden lines of Fe II. The data have been applied to both emission and absorption lines in astrophysical spectra. We make comparisons between experimental, theoretical and astrophysical f-values. We give a general review of the various measurements, and discuss the UV8 multiplet of Fe II around 1610 Å in detail. Title: Experimental oscillator strengths in Th II Authors: Nilsson, H.; Zhang, Z. G.; Lundberg, H.; Johansson, S.; Nordström, B. Bibcode: 2002A&A...382..368N Altcode: We have measured radiative lifetimes of ten Th II levels by using the laser-induced fluorescence technique and branching fractions with Fourier transform spectroscopy. By combining the new branching fractions with a total of 23 lifetimes, from the present work and from measurements by Simonsen et al. (\cite{Simonsen}), absolute oscillator strengths for 180 lines have been derived. Some of these new f-values reported are relevant for radioactive dating of stars. Title: The Strontium Filament within the Homunculus of Eta Carinae Authors: Gull, T. R.; Hartman, H.; Zethson, T.; Johansson, S.; Ishibashi, K.; Davidson, K. Bibcode: 2001AAS...19913501G Altcode: 2001BAAS...33R1505G During a series of HST/STIS observations of Eta Carinae and associated ejecta, we noticed a peculiar emission filament located a few arcseconds north of the central source. While bright in nebular standards, it is submerged in a sea of scattered starlight until moderately high dispersion, long-slit spectroscopy with the STIS (R 8000) brings the emission lines out. The initial spectrum, centered on 6768A with the STIS G750M grating, led to identification of twenty lines from singly-ionized species including [Sr II], [Fe II], [Ti II], [Ni II], [Mn II], and [Co II] (Zethson, etal., 2001, AJ 122, 322). No Balmer emission is detected from this filament and the Fe II 2507,9 lines, known to be pumped by Lyman alpha radiation in other regions near the central source, are not detected. Followup observations have led to detection of hundreds more emission lines from iron group elements in neutral and singly-ionized states. Thus far all are excited by less than 10 eV. This peculiar nebular emission is thought to be due to very intense stellar radiation, stripped of uv flux shortward of Lyman alpha, bathing a neutral structure. We are systematically identifying the many lines (over 90% identified) and measuring line intensities that will then be modeled to determine excitation mechanisms, temperature and density. Two [Sr II] and two Sr II lines have now been measured. Bautista, etal. (in preparation) have modeled the strontium flux ratios and find that large radiation fluxes and/or high strontium abundances may account for the detected emission. These observations were supported by STIS GTO funding and GO funding through the STScI. Title: A model for the origin of the anomalous and very bright UV lines of Fe II in gaseous condensations of the star η Carinae Authors: Johansson, S.; Letokhov, V. S. Bibcode: 2001A&A...378..266J Altcode: We present a qualitative physical model of the origin of two very bright UV lines of Fe II at 2507-2509 Å, present in high-resolution spectra of gaseous condensations (blobs) close to the central star of eta Carinae. The spectra have been obtained with the Hubble Space Telescope (HST). The model is based on a type of Bowen mechanism with selective photoexcitation of Fe II by a broad HLyalpha profile, generated in the HII region and diffusely transferred to the optically thick HI region. The frequency distribution by large Doppler diffusion into the HI region provides a substantial broadening of HLyalpha , which makes it possible to selectively photo-excite short-lived (~1 ns) states at 11.2 eV in Fe II. Within the frame of the present model the intense HLyalpha radiation induces a depletion of the lower, long-lived (~1 ms) level of the strong UV lines by photoionization. The subsequent recombination of Fe III explains the appearance of the ``forest'' of narrow Fe II lines. The possibility of a cyclic process is also discussed, where HLyalpha induces depletion to bound states, which have fast decays in the far-UV to the lower state of the Bowen pumping channel. Title: The FERRUM project: Branching ratios and atomic transition probabilities of Fe II transitions from the 3d6(a 3F)4p subconfiguration in the visible to VUV spectral region Authors: Pickering, J. C.; Johansson, S.; Smith, P. L. Bibcode: 2001A&A...377..361P Altcode: We report measurements of the relative intensities of 81 emission lines of Fe II between 160 nm and 350 nm (62 168 cm-1 to 28 564 cm-1) from 4 levels by high resolution Fourier transform spectrometry, using a Penning discharge lamp as light source. These relative intensities have been used to determine the line branching fractions, which have then been combined with accurate experimental radiative lifetime measurements reported recently to give absolute transition probabilities and oscillator strengths for 81 lines. The accuracy of these f-values is compared with other previous experimental measurements, and with theoretical values. The new transition probabilities will allow accurate determinations of Fe II abundances in a wide variety of astrophysical objects. Tables 2 and 3 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/377/361 Title: Successsive resonance-enhanced two-photon ionization of elements abundant in nebulae. I. Atoms and ions of C, N, and O Authors: Johansson, S.; Letokhov, V. S. Bibcode: 2001A&A...375..319J Altcode: We discuss resonance-enhanced two-photon ionization (RETPI) and present schemes of successive RETPI of the elements C, N, and O in nebulae. RETPI is activated by intrinsic radiation stored in the form of trapped spectral lines of HI, HeI, and HeII in the optically thick nebula. The rate of this two-step photoionization is comparable with or exceeds the low recombination rate of the photoions formed in the process. This leads to an accumulation of photoions and subsequent RETPI until such highly charged ions are formed that they cannot further be ionized in this way by the intrinsic radiation from the strong spectral lines of HI, HeI, and HeII. Title: New laboratory lifetime measurements of U II for the uranium cosmochronometer Authors: Lundberg, H.; Johansson, S.; Nilsson, H.; Zhang, Z. Bibcode: 2001A&A...372L..50L Altcode: We present new measurements of radiative lifetimes for six energy levels of singly ionized uranium, U II, using laser-induced fluorescence technique. One of the levels, 5f36d7p6M13/2 at 26191 cm-1, decays by a transition at 3859.6 Å. This line has recently been observed in the spectrum of the metal-poor star CS1082-001, the first detection of uranium outside the solar system. The lambda 3859 line can be used as the presently most accurate cosmochronometer (Cayrel et al. \cite{Cayrel}). Our value of the lifetime of the 6M13/2 level is 18.6+/-0.7 ns, and it confirms the f-value used in the Nature article by Cayrel et al. (\cite{Cayrel}), which is based on an experimental lifetime of 20+/-5 ns (Chen & Borzileri \cite{Chen}). The new measurement also removes the doubt about the choice between that value and other f-values in the literature, differing by a factor of 3. Adopting the same branching fraction as Chen & Borzileri (\cite{Chen}) for the 3859.6 Å line, we derive a gf-value of 0.68, which is 8% higher than the value used by Cayrel et al. (\cite{Cayrel}). Of significance for the chronometer is also the reduced uncertainty of the radiative lifetime, 4% compared to 25%, and consequently of the f-value, which should decrease the uncertainty in the determination of the stellar age considerably. Title: The FERRUM project: Experimental f-values for 4p-5s transitions in Fe II Authors: Karlsson, H.; Sikstrom, C. M.; Johansson, S.; Li, Z. S.; Lundberg, H. Bibcode: 2001A&A...371..360K Altcode: New measurements of radiative lifetimes of four 3d65s levels in Fe II at about 10 eV are presented along with absolute oscillator strengths for twenty 4p-5s transitions involving the four levels. The experimental measurements are compared with two different sets of theoretical calculations. The lines are of particular interest in the modeling of HLyalpha pumped fluorescence of Fe II in astrophysical plasmas. Title: The Bismuth Abundance in the HGMN Stars χ Lupi and HR 7775 and Improved Atomic Data for Selected Transitions of BI I, BI II, and BI III Authors: Wahlgren, G. M.; Brage, T.; Brandt, J. C.; Fleming, J.; Johansson, S.; Leckrone, D. S.; Proffitt, C. R.; Reader, J.; Sansonetti, C. J. Bibcode: 2001ApJ...551..520W Altcode: High-resolution spectra of the chemically peculiar HgMn stars χ Lupi and HR 7775, obtained with the Hubble Space Telescope/Goddard High Resolution Spectrograph, are investigated for their abundance of bismuth by comparison with LTE synthetic spectrum modeling. HR 7775, previously known from International Ultraviolet Explorer spectra to display strong lines of Bi II, is determined to have bismuth present at an enhancement level of nearly 5 orders of magnitude from the lines Bi II λλ1436, 1902 and Bi III λ1423. The bismuth enhancement for χ Lupi is found to be near a level of 1.5 dex, and an ionization anomaly between Bi+ and Bi++ is apparent. HR 7775 abundance enhancements of the heavy elements platinum, [Pt/H]=4.7 dex, and gold, [Au/H]=3.8 dex, have also been determined. New laboratory measurements for wavelengths and hyperfine structure patterns of Bi I/Bi II/Bi III lines are presented, as well as the results of calculations for hyperfine structure constants and oscillator strengths for selected lines of Bi II and Bi III. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Title: Intensity anomalies in the C IV doublet caused by Fe II fluorescence Authors: Eriksson, M.; Johansson, S.; Wahlgren, G. Bibcode: 2001ASPC..242..325E Altcode: 2001ecom.conf..325E No abstract at ADS Title: Identification of Lines in the Strontium Region of Eta Carinae Authors: Hartman, H.; Zethson, T.; Johansson, S.; Gull, T.; Ishibashi, K.; Davidson, K.; Smith, N. Bibcode: 2001ASPC..242..107H Altcode: 2001ecom.conf..107H No abstract at ADS Title: Mysterious UV Lines of Fe II in the Blob Spectrum of Eta Carinae Authors: Johansson, S.; Letokhov, V. Bibcode: 2001ASPC..242..309J Altcode: 2001ecom.conf..309J No abstract at ADS Title: Fluorescence Lines in Eta Carinae and Other Objects Authors: Johansson, S.; Zethson, T.; Hartman, H.; Letokhov, V. Bibcode: 2001ASPC..242..297J Altcode: 2001ecom.conf..297J No abstract at ADS Title: Cr II Fluorescence in Eta Carinae due to H Lyman Alpha Pumping Authors: Zethson, T.; Hartman, H.; Johansson, S.; Gull, T.; Ishibashi, K.; Davidson, K. Bibcode: 2001ASPC..242...97Z Altcode: 2001ecom.conf...97Z No abstract at ADS Title: Fluorescence Observed in the Ultraviolet Spectrum of RR Telescopii Authors: Hartman, H.; Johansson, S. Bibcode: 2001ASPC..242..361H Altcode: 2001ecom.conf..361H No abstract at ADS Title: Accurate laboratory wavelengths of some ultraviolet lines of Cr, Zn and Ni relevant to time variations of the fine structure constant Authors: Pickering, J. C.; Thorne, A. P.; Murray, J. E.; Litzén, U.; Johansson, S.; Zilio, V.; Webb, J. K. Bibcode: 2000MNRAS.319..163P Altcode: The quality of astronomical spectroscopic data now available is so high that interpretation and analysis are often limited by the uncertainties of the laboratory data base. In particular, the limit with which space-time variations in the fine structure constant α can be constrained using quasar spectra depends on the availability of more accurate laboratory rest wavelengths. We recently measured some transitions in magnesium by high-resolution Fourier transform spectroscopy for this purpose, and we now report measurements on some ultraviolet resonance lines of Znii (2062 and 2026Å), Crii (2066, 2062 and 2056Å) and Niii (1751, 1741, 1709 and 1703Å). Apart from the last line, which is very weak, the uncertainty of these measurements is 0.002cm-1 (0.08må) for the lines around 2000Å and 0.004cm-1 (0.12må) for the lines around 1700Å. Title: The FERRUM project: new experimental and theoretical f-values for 4p-4d transitions in Fe II applied to HST spectra of chi Lupi Authors: Nilsson, H.; Sikström, C. M.; Li, Z. S.; Lundberg, H.; Raassen, A. J. J.; Johansson, S.; Leckrone, D. S.; Svanberg, S. Bibcode: 2000A&A...362..410N Altcode: Radiative lifetimes for six highly excited levels in Fe II have been measured at Lund Laser Centre applying the laser induced fluorescence technique and two-step excitation. The energy levels belong to the even-parity 3d6(5D)4d subconfiguration at about 10 eV. Branching fractions (BF:s) of 29 transitions from these levels to the 3d6(5D)4p subconfiguration at about 5 eV have been measured in the wavelength region 2000-3000 Å with the Lund Fourier Transform Spectrometer. By normalizing the BF:s with the lifetimes we get experimental oscillator strengths for these 29 4p-4d lines. The oscillator strengths are compared with new theoretical calculations using the orthogonal operator technique and applied to high-resolution spectra of the star chi Lupi, recorded with the Hubble Space Telescope. Title: New forbidden and fluorescent Fe III lines identified in HST spectra of eta Carinae Authors: Johansson, S.; Zethson, T.; Hartman, H.; Ekberg, J. O.; Ishibashi, K.; Davidson, K.; Gull, T. Bibcode: 2000A&A...361..977J Altcode: We discuss the origin of eight emission lines in the spectra of gas blobs close to the central star of eta Carinae. The spectra have been obtained with the Goddard High Resolution Spectrograph (GHRS) and the Space Telescope Imaging Spectrograph (STIS) onboard the Hubble Space Telescope. Between 2400 and 2500 Å five narrow lines are identified as new forbidden lines of doubly ionized iron, [Fe III]. We present gA-value data for the corresponding transitions, which combine two different metastable configurations of Fe III. An anomalous intensity of the narrow Fe III line (UV 34) at 1914 Å is explained as fluorescence due to HLyalpha pumping. A level mixing of about 1% increases the f-value of the pumped excitation channel by more than two orders of magnitude, which makes the pumping efficient and the fluorescence significant. We introduce a new designation for fluorescence lines photoexcited by an accidental resonance, eg. < Fe III> in the case of doubly ionized iron. Based on observations with the NASA/ESA Hubble Space Telescope, and supported by grant numbers GO-6501 and GO-7302 from the Space Telescope Science Institute. The STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Title: Ultraviolet fluorescence lines of Fe II observed in satellite spectra of the symbiotic star RR Telescopii Authors: Hartman, H.; Johansson, S. Bibcode: 2000A&A...359..627H Altcode: By examining all emission lines of Fe II in high resolution satellite spectra of the symbiotic star RR Tel we have made a systematic study of fluorescence lines in the ultraviolet wavelength region 1200-3000 Ä. We list 33 energy levels of Fe II that are selectively excited in the stellar system by photons from strong lines of H, He II, Si III, O III, C IV, O V, Ne V, and O VI. All energy levels listed are accompanied by the most probable pumping line. The subsequent decay from the pumped levels results in about 120 fluorescence lines observed in spectra recorded with the International Ultraviolet Explorer and the Hubble Space Telescope. The tables include 9 energy levels and 17 emission lines of Fe II, which are for the first time attributed to fluorescence. In a finding list we also include potential fluorescence lines, which means additional transitions from the pumped energy levels observed in laboratory spectra but not in the stellar spectra. Based on observations by the International Ultraviolet Explorer (IUE) and the Goddard High Resolution Spectrograph (GHRS) onboard the Hubble Space Telescope (HST). Tables 1-5 are only available electronically with the On-Line publication at http://link.springer.de/link/service/00230/ Title: [Sr II] Detected in a Nebular Filament Near Eta Carinae Authors: Gull, T.; Zethson, T.; Hartman, H.; Johansson, S.; Davidson, K.; Ishibashi, K. Bibcode: 2000AAS...196.0508G Altcode: 2000BAAS...32..682G Observations with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope reveal a peculiar emission line region in the close vicinity to Eta Carinae. The lines of [SrII], [MnII], [CoII], [TiII], [NiII] and [FeI] are detected in the 6400-7000A spectral interval at a blue-shifted velocity of 95 km/sec and seem to be associated with a long, narrow filament with dimensions of <0.5" by 1.1". The filament is notable as it is separate both in velocity and structure from the bright emission of the Integral Nebula. This filament is buried within the Homunculus and is not visible in direct images which are dominated by reflection nebulosities. In our literature searches we have found no evidence of strontium emission lines in nebulae. We are aware of permitted transitions of strontium seen in AGB stars. S-processed elements like strontium are not expected in the ejecta of a massive star like Eta Carinae. Detection of [SrII] and the fact that the [NiII], [MnII] and [CoII] lines are unusually strong compared to [FeI] are quite a surprise. It has long been known that nitrogen is overabundant in the ejecta of Eta Carinae. Is this processed material from the present star(s)? Has there been processed material ejected from a more evolved companion? The situation is decidedly mysterious. This research has been supported by NASA through STScI grants and the STIS GTO funding. Title: The FERRUM Project Authors: Johansson, S.; Lundberg, H.; Li, Z.; Nilsson, H.; Sikström, C. M.; Zethson, T.; Hartman, H.; Karlsson, H.; Dolk, L.; Mannervik, S.; Raassen, T.; Leckrone, D. Bibcode: 2000IAUJD...1E..20J Altcode: The FERRUM project aims at improving the database for oscillator strengths in iron group elements with an emphasis on astrophysically important ions. The international collaboration includes experts on experimental, theoretical and observational data. The first results concern Fe II. Experimental radiative lifetimes (LIF technique) for some particular levels of Fe II are combined with experimental (FT spectroscopy) and theoretical branching fractions to obtain absolute oscillator strengths, which are then compared with new theoretical data (orthogonal operator technique). Depending on the agreement complementary theoretical data are included. The new data are tested in stellar spectra (HST, NOT). We have obtained f-values for Fe II lines in the UV and optical regions originating from lower levels with excitation energies in the range 3-10 eV. The lines belong to four different transition arrays. The difference between experimental and theoretical data is of the order of 10%. The new data provide independent and new lines for abundance analysis and a test of LTE conditions in stellar atmospheres. Lifetimes of metastable states are measured at a storage ring, providing the first experimental data for forbidden lines, [Fe II]. Title: Commission 14: Atomic and Molecular Data: (Donnees Atomiques et Moleculaires) Authors: Rostas, F.; Smith, P. L.; Berrington, K. A.; Feautrier, N.; Grevesse, N.; Johansson, S.; Jørgensen, U. G.; Martin, W. C.; Mason, H.; Parkinson, W.; Tchang-Brillet, W. -Ü. L. Bibcode: 2000IAUTA..24..380R Altcode: No abstract at ADS Title: New Zr II oscillator strengths and the zirconium conflict in the HgMn star chi LUPI Authors: Sikström, C. M.; Lundberg, H.; Wahlgren, G. M.; Li, Z. S.; Lynga, C.; Johansson, S.; Leckrone, D. S. Bibcode: 1999A&A...343..297S Altcode: Lifetimes on the sub-nanosecond scale for the levels v(2) D_{3/2}, v(2) F_{3/2} and v(2) F_{5/2} in the 4d5s5p configuration in Zr II have been measured, using the method of laser-induced fluorescence. Combined with branching fractions obtained with the Lund Ultraviolet (UV) Fourier Transform Spectrometer (FTS), experimental oscillator strengths have been derived. From Hubble Space Telescope/Goddard High-Resolution Spectrograph spectra, the zirconium abundance in the HgMn star chi Lupi has been determined from Zr II and Zr III lines. More than an order of magnitude difference in the Zr II abundance has been derived from these ionization stages. The difference is much too large to be explained by uncertainties in the oscillator strengths. Possible explanations of this difference have to be found in the stellar models, such as the influence of non-LTE or diffusion. Title: Strange Velocities in the Equatorial Ejecta of η Carinae Authors: Zethson, T.; Johansson, S.; Davidson, K.; Humphreys, R. M.; Ishibashi, K.; Ebbets, D. Bibcode: 1999ASPC..179..123Z Altcode: 1999ecm..conf..123Z No abstract at ADS Title: Atomic Physics Aspects on Previously and Newly Identified Iron Lines in the HST Spectrum of η Carinae Authors: Johansson, S.; Zethson, T. Bibcode: 1999ASPC..179..171J Altcode: 1999ecm..conf..171J No abstract at ADS Title: Emission line profiles in the spectrum of υ Sgr (poster) Authors: Strid, K.; Kalus, G.; Johansson, S.; Wahlgren, G. M.; Zapadlik, I.; Ardeberg, A.; Lundström, I. Bibcode: 1999anot.conf..252S Altcode: No abstract at ADS Title: The Spectrum and Term Analysis of Co II Authors: Pickering, Juliet C.; Raassen, A. J. J.; Uylings, P. H. M.; Johansson, S. Bibcode: 1998ApJS..117..261P Altcode: High-resolution spectra of singly ionized cobalt have been recorded by Fourier transform spectrometry in the region 1420-33333 Å (70422-3000 cm-1) with cobalt-neon and cobalt-argon hollow cathode lamps as sources. Most of the Co II lines exhibit broadening due to hyperfine structure, but the wavenumber uncertainty for the center of gravity of the strongest lines is less than 0.002 cm-1. Of the previously listed energy levels of Co II, 215 have been revised and six have been discarded. In addition, 171 new levels have been found of which 125 are reported here for the first time. The number of classified lines has doubled with wavenumbers and classifications being presented for 2373 Co II lines, of which 1242 involve the new levels. Title: The Impact of GHRS on Atomic Physics - A Fruitful Collaboration Between Laboratory and Stellar Spectroscopy Authors: Johansson, S.; Leckrone, D. S.; Davidson, K. Bibcode: 1998ASPC..143..155J Altcode: 1998sigh.conf..155J No abstract at ADS Title: Abundances and Isotopic Compositions of Singly Ionized Platinum in Chi LUPI and HR 7775 Authors: Kalus, G.; Johansson, S.; Wahlgren, G. M.; Leckrone, D. S.; Brandt, J. C.; Thorne, A. P. Bibcode: 1998ASPC..143..326K Altcode: 1998sigh.conf..326K No abstract at ADS Title: High-Resolution Observation of B II A1362 in Chi LUPI Authors: Zethson, T.; Johansson, S.; Wahlgren, G. M.; Leckrone, D. S. Bibcode: 1998ASPC..143..339Z Altcode: 1998sigh.conf..339Z No abstract at ADS Title: Atomic Calculations Inspired by the GHRS - gf-Values, Hyperfine Structure Constants, and Isotope Shifts for Heavy Elements Authors: Brage, T.; Proffitt, C. R.; Wahlgren, G. M.; Leckrone, D. S.; Johansson, S. Bibcode: 1998ASPC..143..378B Altcode: 1998sigh.conf..378B No abstract at ADS Title: Very Heavy Elements in the HgMn Star Chi LUPI Authors: Wahlgren, G. M.; Leckrone, D. S.; Brage, T.; Proffitt, C. R.; Johansson, S. Bibcode: 1998ASPC..143..330W Altcode: 1998sigh.conf..330W No abstract at ADS Title: The Abundance of CO in the HgMn Star Chi LUPI Authors: Zethson, T.; Johansson, S.; Wahlgren, C. M.; Pickering, J.; Leckrone, D. S. Bibcode: 1998ASPC..143..334Z Altcode: 1998sigh.conf..334Z No abstract at ADS Title: Oscillator Strengths and the Rhodium Abundance in the HgMn Type Star Chi LUPI Authors: Lundberg, H.; Johansson, S.; Litzen, U.; Wahlgren, C. M.; Leckrone, D. S. Bibcode: 1998ASPC..143..343L Altcode: 1998sigh.conf..343L No abstract at ADS Title: Strange velocities in the equatorial ejecta of Eta Carinae Authors: Davidson, K.; Zethson, T.; Johansson, S.; Ishibashi, K.; Ebbets, D. Bibcode: 1997AAS...191.3406D Altcode: 1997BAAS...29R1261D In 1996--1997 we obtained HST/GHRS and HST/FOS data on locations thought be be in the equatorial ejecta of Eta Carinae. One motivation was a desire to test the age of the equatorial debris-disk, which, according to some evidence, may be younger than the bipolar lobes. In fact, however, the velocities are inconsistent with both of the obvious models. The observed values may indicate the presence of old, slow material, or that the geometrical situation has been misinterpreted, or something else even more bizarre. This is one more instance of an important detail concerning Eta Car that should have been straightforward but which turns out instead to be, essentially, not understood. Title: The Boron Isotope Ratio in HD 76932 Authors: Rebull, L.; Duncan, D.; Johansson, S.; Thorburn, J.; Fields, B.; Schramm, D. Bibcode: 1997AAS...191.1305R Altcode: 1997BAAS...29.1230R Data in the lambda 2090 B region of HD 76932 were obtained using the HST GHRS echelle at a resolution of 90,000. This wavelength region has been previously identified as a likely candidate for observing the (11) B/(10) B isotopic splitting (Johansson et al. 1993). Data presented here provides some constraints on the isotopic ratio, but it is not certain whether or not the line in question is blended with unknown stellar absorption feature(s), making an unambiguous detection of the isotopic ratio impossible. The constraints that can be placed on the isotopic ratio based on these data are discussed. Title: Status of the AMANDA and BAIKAL Neutrino Telescopes Authors: Askebjer, P.; Barwick, S. W.; Bay, R.; Bergström, L.; Bouchta, A.; Carius, S.; Dahlberg, E.; Engel, K.; Erlandsson, B.; Goobar, A.; Gray, L.; Hallgren, A.; Halzen, F.; Heukenkamp, H.; Hulth, P. O.; Hundertmark, S.; Jacobsen, J.; Johansson, S.; Kandhadai, V.; Karle, A.; Liubarsky, I.; Lowder, D.; Mikolajski, T.; Miller, T. C.; Mock, P.; Morse, R.; Nygren, D.; Porrata, R.; Price, P. B.; Richards, A.; Rubinstein, H.; Schneider, E.; Spiering, C.; Streicher, O.; Sun, Q.; Thon, T.; Tilav, S.; Walck, C.; Wiebusch, C.; Wischnewski, R.; Yodh, G.; Belolaptikov, I. A.; Bezrukov, L. B.; Borisovets, B. A.; Budnev, N. M.; Chensky, A. G.; Danilchenko, I. A.; Djilkibaev, Zh. -A. M.; Dobrynin, V. I.; Domogatsky, G. V.; Doroshenko, A. A.; Fialkovsky, S. V.; Gaponenko, O. N.; Garus, A. A.; Gress, T. A.; Ignat'ev, S. B.; Karle, A.; Klabukov, A. M.; Klimov, A. I.; Klimushin, S. I.; Koshechkin, A. P.; Kulepov, V. F.; Kuzmichev, L. A.; Lubsandorzhiev, B. K.; Mikolajski, T.; Milenin, M. B.; Mirgazov, R. R.; Moroz, A. V.; Moseiko, N. I.; Nikiforov, S. A.; Osipova, E. A.; Pandel, D.; Panfilov, A. I.; Parfenov, Yu. V.; Pavlov, A. A.; Petukhov, D. P.; Pocheikin, K. A.; Pokhil, P. G.; Pokolev, P. A.; Rosanov, M. I.; Rubzov, V. Yu.; Sinegovsky, S. I.; Sokalski, I. A.; Spiering, Ch.; Streicher, O.; Tarashansky, B. A.; Thon, T.; Wiebusch, C.; Wischnewski, R. Bibcode: 1997NuPhS..52..256A Altcode: No abstract at ADS Title: Defining the chi LUPI Abundance Peak Among the 5d and 6p Elements Authors: Wahlgren, G. M.; Leckrone, D. S.; Brage, T.; Johansson, S.; Proffitt, C. R. Bibcode: 1996AAS...189.7811W Altcode: 1996BAAS...28.1378W Using the echelle mode of the Hubble Space Telescope/Goddard High Resolution Spectrograph, observations of the extremely sharp-lined HgMn star chi Lupi have provided new insights into the ultraviolet spectrum, both for the purposes of astrophysics and atomic spectroscopy. Testing the diffusion paradigm, generally believed to be the dominant influence in creating the plethora of spectral line strength anomalies in HgMn stars, requires knowledge of the isotope mixture at several ionization stages. Our exciting data for the element mercury provided the impetus to expand our study to include other heavy elements. The high quality GHRS spectra have placed stringent requirements upon the accuracy of the atomic data utilized in our synthetic spectrum analyses. Therefore, we have undertaken a concerted effort to employ both laboratory techniques and theoretical calculations in order to provide such needed data. As a result of this effort we are now able to nearly fully define quantitatively the abundance distribution in this star over the element range defined by the 5d elements tungsten (Z = 74) through mercury (Z = 80) and the 6p elements thallium (Z = 81) through bismuth (Z = 83). We present new abundance determinations for several of these elements, the result of which is to emphasize the presence of a peak in the abundance distribution, defined by the elements platinum (Z = 78) through thallium (Z = 81). This peak, with abundances four to five orders of magnitude greater than the solar system values, is present for the three lowest stages of ionization and is broader than either the r- or s-process peaks that are found in this vicinity of the periodic table in the solar system elemental abundance distribution. Title: Branching Fractions and Oscillator Strengths for Fe II Transitions from the 3d 6( 5D)4p Subconfiguration Authors: Bergeson, S. D.; Mullman, K. L.; Wickliffe, W. E.; Lawler, J. E.; Litzen, U.; Johansson, S. Bibcode: 1996ApJ...464.1044B Altcode: New experimental branching fractions and transition probabilities are reported for 56 transitions in Fe II. The branching fractions are measured with a Fourier transform spectrometer and also with a high-resolution grating spectrometer on an optically thin hollow cathode discharge. Highly accurate experimental radiative lifetimes from the recent literature provide the normalization required to convert our branching fractions into absolute transition probabilities. Results are compared with experimental and theoretical values in the literature. Our new transition probabilities will establish the absolute scale for relative absorption oscillator strengths of vacuum ultraviolet lines measured using a new high-sensitivity absorption experiment at the University of Wisconsin. Title: Is there a Dichromatic UV Laser in Eta Carinae? Authors: Johansson, S.; Davidson, K.; Ebbets, D.; Weigelt, G.; Balick, B.; Frank, A.; Hamann, F.; Humphreys, R. M.; Morse, J.; White, R. L. Bibcode: 1996swhs.conf..361J Altcode: No abstract at ADS Title: Investigating fluorescence mechanisms in the atmosphere of the cool, supergiant star alpha ORI Authors: Wahlgren, G. M.; Johansson, S. Bibcode: 1996ASPC..109..551W Altcode: 1996csss....9..551W No abstract at ADS Title: Term analysis of a complex spectrum. Authors: Johansson, S. Bibcode: 1996PhST...65....7J Altcode: A term analysis of a complex spectrum is like a giant jigsaw puzzle with pieces of different sizes, shapes, colours, etc., and the result is a picture of the atomic structure of an atom or ion having several valence electrons. This knowledge of the atomic structure tests the theoretical model of complex atoms and theoretical calculations of various atomic parameters. These atomic parameters are fundamental ingredients in, e.g. abundance analyses of astrophysical spectra. The author discusses the atomic structure of transition group elements based on term analyses of their spectra. He gives examples from Fe II and Zr II. The strong coupling to high-resolution stellar spectroscopy, in particular in the satellite ultraviolet and near-infrared wavelength regions, is emphasized. Missing atomic data for transition elements is still the main reason for missing opacity in stellar spectra, calculated from stellar model atmospheres. Title: Atomic Data for High Resolution Stellar Spectroscopy: A Review Authors: Johansson, S.; Leckrone, D. S. Bibcode: 1996ASPC..108..113J Altcode: 1996mass.conf..113J No abstract at ADS Title: Stellar chemical abundances with the GHRS. Authors: Leckrone, D. S.; Johansson, S.; Wahlgren, G. M.; Proffitt, C. R.; Brage, T. Bibcode: 1996PhST...65..110L Altcode: The accurate quantitative analysis of high resolution ultraviolet spectra of ultra-sharp-lined, early-type, chemically peculiar stars, obtained with the Goddard High Resolution Spectrograph on the Hubble Space Telescope, has been made possible by the synergism between state-of-the-art astrophysics and state-of-the-art atomic spectroscopy. The authors illustrate this with several examples, including the discovery of spin-forbidden "parasite" transitions of Fe II, the first observations of hyperfine components and isotopic shifts of stellar lines of thallium, and measurements of the photospheric abundances of a large number of normally trace elements. Title: High excitation Rydberg levels of Fe I from the ATMOS solar spectrum at 2.5 and 7 μm. Authors: Schoenfeld, W. G.; Chang, E. S.; Geller, M.; Johansson, S.; Nave, G.; Sauval, A. J.; Grevesse, N. Bibcode: 1995A&A...301..593S Altcode: The quadrupole-polarization theory has been applied to the 3d^6^4s(^6^D)4f and 5g subconfigurations of Fe I by a parametric fit, and the fitted parameters are used to predict levels in the 6g and 6h subconfigurations. Using the predicted values, we have computed the 4f-6g and 5g-6h transition arrays and made identifications in the ATMOS infrared solar spectrum. The newly identified 6g and 6h levels, based on ATMOS wavenumbers, are combined with the 5g levels and found to agree with the theoretical values with a root mean-squared-deviation of 0.042cm^-1^. Our approach yields a polarizability of 28.07 a_o_^3^and a quadrupole moment of 0.4360+/-0.0010ea_o_^2^for Fe II, as well as an improved ionization potential of 63737.700+/-0.010cm^-1^ for Fe I. Title: Fluorescence lines of MnII in the red spectrum of η Carinae. Authors: Johansson, S.; Wallerstein, G.; Gilroy, K. K.; Joueizadeh, A. Bibcode: 1995A&A...300..521J Altcode: Five emission lines in the wavelength region 6122-6132 A in the spectrum of η Carinae are identified as the 4d ^5^D-4f ^5^F multiplet of Mn^44^Sc II. These are the only high-excitation lines of Mn^44^Sc II present in the spectrum. The upper levels of the multiplet are most likely populated through photoexcitation by an accidental coincidence in wavelength between the ultraviolet multiplets UV 15 of Mn^44^Sc II and UV 5 of Si^44^Sc II. Improved laboratory wavelengths for the Mn^44^Sc II lines are presented. Title: Initial Analysis of Coincident Events Between the SPASE and AMANDA Detectors Authors: Miller, T.; Beaman, J.; Evenson, P. A.; Gaisser, T. K.; Hart, S.; Lloyd-Evans, J.; Martello, D.; Ogden, P.; Petrakis, J.; Stanev, Todor; Watson, A. A.; Askebjer, P.; Barwick, S. W.; Bergström, L.; Bouchta, A.; Carius, S.; Erlandsson, B.; Goobar, A.; Gray, L.; Hallgren, L. A.; Halzen, F.; Hulth, P. O.; Jacobsen, J.; Johansson, S.; Kandhadai, V.; Liubarsky, I.; Lowder, D. M.; Miller, T.; Mock, P.; Morse, R.; Porrata, R.; Price, P. B.; Richards, A.; Rubinstein, H.; Sun, Q.; Tilav, S.; Walck, C.; Yodh, G. Bibcode: 1995NuPhS..43..245M Altcode: We report on the status of the SPASE-AMANDA coincidence experiment. Title: VizieR Online Data Catalog: New multiplet table for FeI (Nave+, 1994) Authors: Nave, G.; Johansson, S.; Learner, R. C. M.; Thorne, A. P.; Brault, J. W. Bibcode: 1995yCat..20940221N Altcode: We have recorded spectra of iron-neon and iron-argon hollow cathode lamps in the region 1700A-5um (59,000-2000cm-1), with Fourier transform (FT) spectrometers at the National Solar Observatory, Tucson, Arizona, and Imperial College, London, UK, and with a high-resolution grating spectrograph at the National Institute of Standards and Technology, Gaithersburg, Maryland. The uncertainty of the strongest lines in the FT spectra is less than 0.002cm-1 (0.2mA at 3000A; 8mA at 2um). Pressure- and current-dependent shifts are less than 0.001cm-1 for transitions between low-lying levels, increasing to 0.006cm-1 for transitions between the most highly excited levels. We report 28 new energy levels of Fe I and revised values of another 818 levels. We have identified 9501 lines as due to 9759 transitions in Fe I, and these are presented in the form of a new multiplet table and finding list. This compares with the ~5500 lines due to 467 energy levels in the multiplet tables of Moore (1950, NBS Circ., No.488 and 1959, NBS Tech. note 30). The biggest increase is in the near-ultraviolet and near infrared, and many of the new lines are present in the solar spectrum. Experimental log (gf) values are included where they are available. A further 125 unidentified lines due to Fe I are given. (4 data files). Title: Optical Properties of the South Pole Ice at Depths Between 0.8 and 1 Kilometer Authors: Askebjer, P.; Barwick, S. W.; Bergstrom, L.; Bouchta, A.; Carius, S.; Coulthard, A.; Engel, K.; Erlandsson, B.; Goobar, A.; Gray, L.; Hallgren, A.; Halzen, F.; Hulth, P. O.; Jacobsen, J.; Johansson, S.; Kandhadai, V.; Liubarsky, I.; Lowder, D.; Miller, T.; Mock, P. C.; Morse, R.; Porrata, R.; Price, P. B.; Richards, A.; Rubinstein, H.; Schneider, E.; Sun, Q.; Tilav, S.; Walck, C.; Yodh, G. Bibcode: 1995Sci...267.1147A Altcode: The optical properties of the ice at the geographical South Pole have been investigated at depths between 0.8 and 1 kilometer. The absorption and scattering lengths of visible light (~515 nanometers) have been measured in situ with the use of the laser calibration setup of the Antarctic Muon and Neutrino Detector Array (AMANDA) neutrino detector. The ice is intrinsically extremely transparent. The measured absorption length is 59 ± 3 meters, comparable with the quality of the ultrapure water used in the Irvine-Michigan-Brookhaven and Kamiokande proton-decay and neutrino experiments and more than twice as long as the best value reported for laboratory ice. Because of a residual density of air bubbles at these depths, the trajectories of photons in the medium are randomized. If the bubbles are assumed to be smooth and spherical, the average distance between collisions at a depth of 1 kilometer is about 25 centimeters. The measured inverse scattering length on bubbles decreases linearly with increasing depth in the volume of ice investigated. Title: Measurements of the Absorption Length of the Ice at the South Pole in the Wavelength Interval 410 nm to 610 nm Authors: Erlandsson, B.; Askebjer, P.; Barwick, S. W.; Bergström, L.; Bouchta, A.; Carius, S.; Goobar, A.; Gray, L.; Hallgren, A.; Halzen, F.; Heukenkamp, H.; Hulth, P. O.; Jacobsen, J.; Johansson, S.; Kandhadai, V.; Karle, A.; Liubarsky, I.; Lowder, D.; Miller, T. C.; Mock, P. C.; Morse, R.; Porrata, R.; Price, P. B.; Richards, A.; Rubinstein, H.; Spiering, C.; Sun, Q.; Thon, T.; Tilav, S.; Walck, C.; Wishnewski, R.; Yodh, G. Bibcode: 1995ICRC....1.1039E Altcode: 1995ICRC...24a1039E No abstract at ADS Title: Status and Capabilities of AMANDA-94 Authors: Mock, P. C.; Askebjer, P.; Barwick, S. W.; Bergström, L.; Bouchta, A.; Carius, S.; Erlandsson, B.; Goobar, A.; Gray, L.; Hallgren, A.; Halzen, F.; Heukenkamp, H.; Hulth, P. O.; Jacobsen, J.; Johansson, S.; Kandhadai, V.; Karle, A.; Liubarsky, I.; Lowder, D.; Miller, T. C.; Morse, R.; Porrata, R.; Price, P. B.; Richards, A.; Rubenstein, H.; Spiering, C.; Sun, Q.; Thon, T.; Tilav, S.; Walck, C.; Wischnewski, R.; Yodh, G. Bibcode: 1995ICRC....1..758M Altcode: 1995ICRC...24a.758M No abstract at ADS Title: Analysis of High-Resolution Laboratory Spectra of Iron and Identification of Fe I Lines in the Solar Spectrum Authors: Nave, G.; Johansson, S. Bibcode: 1995ASPC...81..197N Altcode: 1995lahr.conf..197N No abstract at ADS Title: SPASE -- AMANDA Coincidences At The South Pole Authors: Miller, T. C.; Gaisser, T. K.; Hart, S.; Lloyd-Evans, J.; Martello, D.; Petrakis, J.; Stanev, T.; Watson, A. A.; Askebjer, P.; Barwick, S. W.; Bergstrom, L.; Bouchta, A.; Carius, S.; Erlandsson, B.; Goobar, A.; Gray, L.; Hallgren, A.; Halzen, F.; Heukenkamp, H.; Hulth, P. O.; Jacobsen, J.; Johansson, S.; Kandhadai, V.; Karle, A.; Liubarksky, I.; Lowder, D.; Miller, T. C.; Mock, P.; Porrata, R.; Price, P. B.; Richards, A.; Rubinstein, H; Schneider, E.; Spiering, C.; Sun, Q.; Tilav, S.; Walck, C.; Wischnewski, R.; Yodh, G. Bibcode: 1995ICRC....2..768M Altcode: 1995ICRC...24b.768M No abstract at ADS Title: Indirect Evidence for Long Absorption Lengths in Antarctic Ice Authors: Tilav, S.; Askebjer, P.; Barwick, S. W.; Bergström, L.; Bouchta, A.; Carius, S.; Erlandsson, B.; Goobar, A.; Gray, L.; Hallgren, A.; Halzen, F.; Heukenkamp, H.; Hulth, P. O.; Jacobsen, J.; Johansson, S.; Kandhadai, V.; Karle, A.; Liubarsky, I.; Lowder, D. M.; Martello, D.; Miller, T. C.; Mock, P. C.; Morse, R.; Porrata, R.; Price, P. B.; Richards, A.; Rubenstein, H.; Spiering, C.; Sun, Q.; Thon, T.; Walck, C.; Wishnewski, R.; Yodh, G. Bibcode: 1995ICRC....1.1011T Altcode: 1995ICRC...24a1011T No abstract at ADS Title: Isotope Shift in Pt II Observed in Laboratory FTS Spectra Authors: Kalus, G. M.; Johansson, S.; Thorne, A. P.; Leckrone, D. S.; Wahlgren, G. M. Bibcode: 1995ASPC...81..239K Altcode: 1995lahr.conf..239K No abstract at ADS Title: Improved Wavelengths and Extended Analysis of TI II Authors: Zapadlik, I.; Johansson, S.; Litzen, U. Bibcode: 1995ASPC...81..237Z Altcode: 1995lahr.conf..237Z No abstract at ADS Title: The Design of a Neutrino Telescope Using Natural Deep Ice as a Particle Detector Authors: Gray, L.; Askebjer, P.; Barwick, S. W.; Bergström, L.; Bouchta, A.; Carius, S.; Erlandsson, B.; Goobar, A.; Hallgren, A.; Halzen, F.; Heukenkamp, H.; Hulth, P. O.; Jacobsen, J.; Johansson, S.; Kandhadai, V.; Karle, A.; Liubarsky, I.; Lowder, D. M.; Miller, T. C.; Mock, P. C.; Morse, R.; Porrata, R.; Price, P. B.; Richards, A.; Rubenstein, H.; Spiering, C.; Sun, Q.; Tilav, S.; Thon, T.; Walck, C.; Wishnewski, R.; Yodh, G. Bibcode: 1995ICRC....1..816G Altcode: 1995ICRC...24a.816G No abstract at ADS Title: Optical Properties of South Pole Ice for Neutrino Astrophysics Authors: Price, P. B.; Askebjer, P.; Barwick, S. W.; Bergstrom, L.; Bouchta, A.; Carius, S.; Erlandsson, B.; Goobar, A.; Gray, L.; Hallgreen, A.; Halzen, F.; Heukenkamp, H.; Hulth, P. O.; Jacobsen, J.; Johansson, S.; Kandhadai, V.; Karle, A.; Liubarsky, I.; Lowder, D. M.; Miller, T. C.; Mock, P. C.; Morse, R.; Porrata, R.; Richards, A.; Rubenstein, H.; Spiering, C.; Sun, Q.; Tilav, S.; Walck, C.; Westphal, A. J.; Wischnewski, R.; Yodh, G. Bibcode: 1995ICRC....1..777P Altcode: 1995ICRC...24a.777P No abstract at ADS Title: Remote Surveys of AMANDA Authors: Askebjer, P.; Barwick, S. W.; Bergström, L.; Bouchta, A.; Carius, S.; Engel, K.; Erlandsson, B.; Gaisser, T. K.; Goobar, A.; Gray, L.; Hallgren, A.; Halzen, F.; Heukenkamp, H.; Hulth, P. O.; Jacobsen, J.; Johansson, S.; Kandhadai, V.; Karle, A.; Liubarsky, I.; Lowder, D. M.; Martello, D.; Miller, T. C.; Mock, P. C.; Morse, R.; Porrata, R.; Price, P. B.; Richards, A.; Rubenstein, H.; Spiering, C.; Sun, Q.; Thon, T.; Tilav, S.; Walck, C.; Wishnewski, R.; Yodh, G. Bibcode: 1995ICRC....1.1009A Altcode: 1995ICRC...24a1009A No abstract at ADS Title: High Resolution Spectroscopy of Singly Ionized Transition Elements Authors: Johansson, S. Bibcode: 1995ASPC...81..151J Altcode: 1995lahr.conf..151J No abstract at ADS Title: A New Multiplet Table for Fe i Authors: Nave, G.; Johansson, S.; Learner, R. C. M.; Thorne, A. P.; Brault, J. W. Bibcode: 1994ApJS...94..221N Altcode: We have recorded spectra of iron-neon and iron-argon hollow cathode lamps in the region 1700 A-5 micrometers (59,000-2000/cm), with Fourier transform (FT) spectrometers at the National Solar Observatory, Tucson, Arizona, and Imperial College, London, UK, and with a high-resolution grating spectrograph at the National Institute of Standards and Technology, Gaithersburg, Maryland. The uncertainty of the strongest lines in the FT spectra is less than 0.002/cm (0.2 mA at 3000 A; 8 mA at 2 micrometers). Pressure- and current-dependent shifts are less than 0.001/cm for transitions between low-lying levels, increasing to 0.006 cm-1 for transitions between the most highly excited levels. We report 28 new energy levels of Fe I and revised values of another 818 levels. We have identified 9501 lines as due to 9759 transitions in Fe I, and these are presented in the form of a new multiplet table and finding list. This compares with the approximately 5500 lines due to 467 energy levels in the multiplet tables of Moore (1950, 1959). The biggest increase is in the near-ultraviolet and near infrared, and many of the new lines are present in the solar spectrum. Experimental log (gf) values are included where they are available. A further 125 unidentified lines due to Fe I are given. The tables are also available in computer-readable form. Title: UV-spektra från Hubble-teleskopet avslöjar en stjärna i Vargen som lagrar tunga isotoper av mycket tunga grundämnen. Authors: Johansson, S. E.; Leckrone, D. S.; Wahlgren, G. M. Bibcode: 1994ATi....27..113J Altcode: UV spectra from the Hubble Space Telescope reveal a star that stores heavy isotopes of very heavy elements. Atomic and plasma physics arguments for UV spectroscopy from space borne observatories are given. As an example, the authors discuss the analysis of high resolution spectra of the chemically peculiar star χ Lupi, obtained with the Hubble Space Telescope, in terms of identification of spectral lines of very heavy elements. Title: Analysis of the 3d 64 s( 6D)4f--5g Supermultiplet of Fe i in Laboratory and Solar Infrared Spectra Authors: Johansson, S.; Nave, G.; Geller, M.; Sauval, A. J.; Grevesse, N.; Schoenfeld, W. G.; Change, E. S.; Farmer, C. B. Bibcode: 1994ApJ...429..419J Altcode: 1994astro.ph..4050J The combined laboratory and solar analysis of the highly-excited subconfigurations 4f and 5g of Fe I has allowed us to classify 87 lines of the 4f-5g supermultiplet in the spectral region 2545-2585 cm-1. The level structure of these JK-coupled configurations is predicted by semiempirical calculations and the quadrupolic approximation. Semiempirical gf-values have been calculated and are compared to gf values derived from the solar spectrum. The solar analysis has shown that these lines, which should be much less sensitive than lower excitation lines to departures from LTE and to temperature uncertainties, lead to a solar abundance of iron which is consistent with the meteoritic value (A_Fe = 7.51). Title: A glimpse into the post-COSTAR GHRS: detections of As II and Bi II in the UV spectrum of the HgMn star χ Lupi. Authors: Wahlgren, G. M.; Brage, T.; Gilliland, R. L.; Johansson, S.; Leckrone, D. S.; Lindler, D. J. Bibcode: 1994BAAS...26..869W Altcode: No abstract at ADS Title: A New Multiplet Table for Fe Authors: Nave, I. G.; Johansson, S.; Learner, R. C. M.; Thorne, A. P.; Brault, J. W. Bibcode: 1994astro.ph..4049N Altcode: We have recorded spectra of iron-neon and iron-argon hollow cathode lamps in the region 1700A -- 5um (59000 -- 2000cm-1), with Fourier transform (FT) spectrometers at the National Solar Observatory, Tucson, Arizona, U.S.A. and Imperial College, London, U.K., and with a high resolution grating spectrograph at the National Institute of Standards and Technology, Gaithersburg, U.S.A. The uncertainty of the strongest lines in the FT spectra is <0.002cm-1 (0.2mA at 3000A; 8mA at 2um). Pressure and current-dependent shifts are <0.001cm-1 for transitions between low lying levels, increasing to 0.006 cm-1 for transitions between the most highly excited levels. We report 28 new energy levels of Fe I and revised values of another 818 levels. We have identified 9501 lines as due to 9759 transitions in Fe I, and these are presented in the form of a new multiplet table and finding list. This compares with the 5500 lines due to 467 energy levels in the multiplet tables of Moore (1950, 1959). The biggest increase is in the near ultraviolet and near infra-red, and many of the new lines are present in the solar spectrum. Experimental log(gf) values are included where available. A further 125 unidentified lines due to Fe I are given. Title: Analysis of Very High Excitation Fe I Lines (4f - 5g) in the Solar Infrared Spectrum Authors: Johansson, S.; Nave, G.; Geller, M.; Sauval, A. J.; Grevesse, N. Bibcode: 1994IAUS..154..543J Altcode: No abstract at ADS Title: Highly-excited levels of Fe I obtained from laboratory and solar Fourier transform and grating spectra. II. Laboratory and solar identifications Authors: Nave, G.; Johansson, S. Bibcode: 1993A&AS..102..269N Altcode: New identifications of ∼2200 Fe I lines between 1700 Å and 5 μm (59 000 cm-1 -2000 cm-1) due to highly-excited configurations are presented. These have been observed in hollow cathode lamps using Fourier transform and grating spectroscopy. About 1700 of the lines have been observed in the solar spectrum. A companion paper presents the experimental energy levels. Title: VizieR Online Data Catalog: Lab. and solar highly-excited levels of Fe I (Nave+ 1993) Authors: Nave, G.; Johansson, S. Bibcode: 1993yCat..41020269N Altcode: New identifications of about 2200 FeI lines between 170nm and 5μm (59000 to 2000 cm-1) due to highly-excited configurations are presented. These have been observed in hollow cathode lamps using Fourier transform and grating spectroscopy. About 1700 if the lines have been observed in the solar spectrum. A companion paper presents the experimental energy levels. (1 data file). Title: Highly-excited levels of Fe i obtained from laboratory and solar Fourier transform and grating spectra. 1. Energy levels Authors: Nave, G.; Johansson, S. Bibcode: 1993A&A...274..961N Altcode: 86 new levels due to the highly-excited configurations 3d64s(6D)nl, 3d64s(6D)nl, 3d64s(4D)nl, and 3d7(4F)nl of Fe I have been established using visible and infra-red Fourier transform spectra of iron-neon and iron-argon hollow cathodes. 110 previously reported levels have also been revised to an accuracy of 0.003-0.005 cm-1. The levels were confirmed by comparison with ultraviolet spectra measured with a 1O.7m grating spectrograph. A companion paper presents the identified lines in both laboratory and solar spectra. Title: High resolution UV stellar spectroscopy with the HST/GHRS, challenges and opportunities for atomic physics. Authors: Leckrone, D. S.; Johansson, S.; Wahlgren, G. M.; Adelman, S. J. Bibcode: 1993PhST...47..149L Altcode: The Goddard High Resolution Spectrograph (GHRS) on the Hubble Space Telescope (HST) is producing ultraviolet spectra of unprecedented resolution and photometric quality. The authors illustrate this with observations of the ultra-sharp-lined, chemically peculiar B-type star, χ Lupi. The photosphere of this star is rich in heavy elements, and its UV spectrum is replete with transitions of species not commonly observed in astrophysical spectra. It is an excellent "laboratory" for atomic spectroscopy. Kurucz's comprehensive calculations of transition probabilities for the iron-group and other elements provides a reasonable starting point for theoretical spectrum synthesis. However, evidence is found of large systematic errors in his data base for transitions from particular energy levels in Fe II, Cr II, Co II, and other ions. Title: Fluorescence lines in ultraviolet spectra of stars Authors: Johansson, S.; Hamann, F. W. Bibcode: 1993PhST...47..157J Altcode: We discuss the presence of fluorescence lines that appear in stellar spectra in the satellite ultraviolet region between 1200 and 3200 Å. Strong lines in partial multiplets result from a selective excitation, which in most cases is due to accidental wavelength coincidences. The prototype of photoexcitation by accidental resonance (PAR) is the classical Bowen mechanism. Photoexcitation by continuum radiation (PCR) is another source of selective population.

Besides a brief review of ultraviolet fluorescence lines identified in spectra of symbiotic stars and cool stars we discuss in detail two emission peaks at 2506-2508 Å. We give three different explanations for the appearance of this feature in IUE spectra of three different objects: RR Tel, η Car and KQ Pup. In connection to these lines we also discuss primary and secondary cascades in the near-infrared observed in high-resolution spectra. Comments are made on the strong Fe II line at 9997 Å. Title: Using HST / GHRS Echelle Spectra as Templates for IUE Data Analysis Authors: Wahlgren, G. M.; Leckrone, D. S.; Johansson, S.; Rosberg, M. Bibcode: 1993ASPC...44..121W Altcode: 1993pvnp.conf..121W; 1993IAUCo.138..121W No abstract at ADS Title: Ly Alpha Pumping of Fe II in Quasars and AGN Authors: Hamann, F.; Ferland, G.; Johansson, S. Bibcode: 1992AAS...181.3512H Altcode: 1992BAAS...24Q1174H No abstract at ADS Title: Lyα pumping of Fe II in quasars and AGN. Authors: Hamann, F.; Ferland, G.; Johansson, S. Bibcode: 1992BAAS...24R1174H Altcode: No abstract at ADS Title: Fe II Emission from Qussars and AGN Authors: Hamann, F.; Ferland, G.; Pradhan, A.; Johansson, S. Bibcode: 1992AAS...179.6315H Altcode: 1992BAAS...24R.682H No abstract at ADS Title: Detection of high energy neutrinos in PAN Authors: Bergström, L.; Johansson, S. Bibcode: 1992hena.conf..309B Altcode: No abstract at ADS Title: Fe II emission from quasars and AGN. Authors: Hamann, F.; Ferland, G.; Pradhan, A.; Johansson, S. Bibcode: 1991BAAS...23R1424H Altcode: No abstract at ADS Title: Measuring the Energy of Multi-TeV Muons with a Water Cerenkov Detector Authors: Johansson, S. Bibcode: 1991ICRC....4..552J Altcode: 1991ICRC...22d.552J No abstract at ADS Title: New Identifications of Highly-Excited Fe I Lines Around 4μm in Cool Stars Authors: Johansson, S.; Nave, G.; Learner, R. C. M.; Thorne, A. P. Bibcode: 1991isrs.conf..189J Altcode: No abstract at ADS Title: High Resolution Atomic Spectroscopy in the Infrared and its Application to Astrophysics Authors: Johansson, S. Bibcode: 1991isrs.conf...87J Altcode: No abstract at ADS Title: New Identifications of Highly-Excited Fe I Lines Around 4 μm in Cool Stars Authors: Johansson, S.; Rosberg, M.; Hamann, F. Bibcode: 1991isrs.conf..107J Altcode: No abstract at ADS Title: The Fe II Fluorescence Emission in UV Spectra of Symbiotics and Nuclei of Planetary Nebulae Authors: Bruhweiler, F.; Feibelman, W. A.; Johansson, S. Bibcode: 1990BAAS...22R1205B Altcode: No abstract at ADS Title: Gas dynamics, accretion and evolution of Algols: initial results for three representative systems Authors: Gimenez, A.; Gonzalez-Riestra, R.; Guinan, E. F.; Kondo, Y.; McCluskey, G. E.; Bradstreet, D. H.; McCook, G. P.; Dorren, J. D.; Johansson, S.; Sahade, J. Bibcode: 1990ESASP.310..383G Altcode: 1990eaia.conf..383G No abstract at ADS Title: Fe II lines from laboratory and astrophysical sources. Authors: Baschek, B.; Johansson, S. Bibcode: 1990JQSRT..44..215B Altcode: No abstract at ADS Title: High Resolution Ultraviolet Stellar Spectroscopy From Space Observatories - Atomic Physics and Astrophysics Authors: Leckrone, D. S.; Johansson, S.; Kurucz, R. L.; Adelman, S. J. Bibcode: 1989BAAS...21.1198L Altcode: No abstract at ADS Title: Complex atoms in astrophysical spectra. Authors: Johansson, S.; Cowley, C. R. Bibcode: 1988JOSAB...5.2264J Altcode: 1988OSAJB...5.2264J The paper reviews the spectroscopic work on atomic lines and energy levels in neutral and singly and doubly ionized iron-group elements during the past 35 years. The completeness of the analysis of these spectra was graded and they were compared with the data included in the multiplet tables of Moore (1962, 1972). Specific comments are given on each spectrum. New demands for atomic data resulting from high-resolution spectroscopy of peculiar stars and observations from above the earth's atmosphere are discussed. The atomic data that have become available since Moore's compilations are referred to here as second-generation spectra. Title: Absorption spectra of Fe I in the 1550 - 3215-Å region. Authors: Brown, C. M.; Ginter, M. L.; Johansson, S.; Tilford, S. G. Bibcode: 1988JOSAB...5.2125B Altcode: 1988OSAJB...5.2125B The high-dispersion absorption spectrum of Fe I is reported in the 1550-3215-A region. Included are wavelengths of about 3000 observed spectral features, improved spectral assignments, 248 new energy levels, and a value for the ionization potential of 63 737/cm obtained from extrapolation of Rydberg series. Improved wavelengths for several hundred V I and Ti I spectral lines determined on the same spectrograms as the iron data also are presented. Title: Doubly Excited Feii Lines in the A-Star 21-PEGASI Authors: Adam, J.; Baschek, B.; Brage, T.; Nilsson, A. E.; Johansson, S. Bibcode: 1988ASSL..138..243A Altcode: 1988IAUCo..94..243A; 1988pffl.proc..243A The majority of about 120 ultraviolet iron lines, among them strong lines around 1850 Å, which have recently been identified as transitions from doubly excited levels in Fe II during a new investigation of the hollow-cathode spectrum of iron, coincide with absorption lines in the high-resolution IUE spectrum of the sharp-lined A star 21 Pegasi. Model atmosphere calculations of the line strengths confirm the identification for about one third of the lines. Title: Accidental Degeneracy Between Doubly Excited States in Feii Authors: Brage, T.; Nilsson, A. E.; Johansson, S.; Baschek, B.; Adams, J. Bibcode: 1988ASSL..138...63B Altcode: 1988IAUCo..94...63B; 1988pffl.proc...63B No abstract at ADS Title: Future Laboratory Work in Feii Authors: Johansson, S. Bibcode: 1988ASSL..138..313J Altcode: 1988pffl.proc..313J; 1988IAUCo..94..313J No abstract at ADS Title: On regularities in complex spectra of iron group elements and their dominance in stellar spectra Authors: Johansson, S. Bibcode: 1987PhyS...36...99J Altcode: Regularities in complex spectra of iron group elements are illustrated as regards iso-electronic and iso-ionic sequences as well as iso-elemental comparisons. Determination of series limits and ionization potentials in spectra of doubly ionized iron-group elements from iso-ionic plots and Ritz diagrams is discussed. New data for doubly-excited states in Fe I are deduced from iso-ionic regularities in the binding energy of two-electron configurations nl2 relative to a core of d-electrons. New spectroscopic data for Fe I are presented together with a discussion of the dominance of the Fe I spectrum in the sun. Title: Ultraviolet Doubly Excited Fe II Lines in the Laboratory and in the A-Type Star 21 Pegasi Authors: Adam, J.; Baschek, B.; Johansson, S.; Nilsson, A. E.; Brage, T. Bibcode: 1987ApJ...312..337A Altcode: During a new investigation of the UV hollow-cathode spectrum of iron, some 120 lines were identified, among them strong lines around 1850 A, as transitions from doubly excited levels in Fe II. A combination of selective population by charge-transfer processes in the laboratory source and of a strong configuration interaction is probably the cause of unexpectedly large intensities of a great number of lines. The new energy levels and calculated oscillator strengths for the newly identified transitions are presented. Most of the new lines coincide with absorption lines in the high-resolution IUE spectrum of the sharp-lined A star 21 Pegasi. For about one-third of them, located mostly in the region 1750-1900 A, the identifications are confirmed by modal atmosphere calculations. For the remaining coincidences the stellar line is probably blended with another contributor. Title: The absorption spectrum of titanium between 1900 Å and 2315 Å Authors: Forsberg, P.; Johansson, S.; Smith, P. L. Bibcode: 1986PhyS...34..759F Altcode: The absorption spectrum of Ti I has been analyzed in the region 1900-2315 A. The list contains 219 lines, of which 64 have been identified as transitions between the ground term and terms of the odd configurations (3d + 4s)3 np (n = 4, 5). Sixteen new energy levels have been found, and three odd level values have been revised. Most of the identified Ti I lines are present in the solar spectrum. Title: The identification of high-level transitions of Fe II in stellar spectra. Authors: Johansson, S.; Cowley, C. R. Bibcode: 1984A&A...139..243J Altcode: Positive identifications are made in four B and A-type stellar spectra of lines from 3d6(5D)4d-3d6(5D)4f transitions in Fe II. The lowest levels of the 4d terms have excitation energies of 10.3 eV, while those of the 4f terms are at 12.8 eV. Numerous features that were previously unidentified in B and A stars may now be explained. The obvious presence of such transitions makes it probable that many other high-level transitions are present in stellar spectra. Some of these transitions have not yet been identified in laboratory studies analyses, but they could be of considerable importance in the chemical analyses of stellar atmospheres. Title: Selective excitation of Fe II in the laboratory and late-type stellaratmospheres. Authors: Johansson, S.; Jordan, C. Bibcode: 1984MNRAS.210..239J Altcode: Low resolution spectra of cool giants and supergiants observed with the International Ultraviolet Explorer (IUE) satellite contain emission features for which it has been difficult to establish unambiguous identifications. High resolution spectra of RR Tel and Beta Gru (M 3 II) show lines which can be definitely attributed to Fe II. The presence of particular transitions and absence of others suggests that the source of excitation for levels with excitation energy around 10 eV is emission in the H Ly alpha line which is strong and broad in the cool giants and supergiants. New laboratory spectra confirm the excitation route for Ly alpha pumping to a further 4G0 level at about 13 eV, which decays to give the strong feature at 1870 A observed at low spectral resolution in several cool stars. Title: New Fe II lines in IUE spectra of stars. Authors: Johansson, S. Bibcode: 1984ESASP.218..307J Altcode: 1984iue..conf..307J The never-ceasing need for more atomic data of Fe II for astrophysical purposes is discussed in terms of present state and future work on the term analysis of this spectrum. More data already exist and an extended analysis of laboratory data has just started. Special excitation conditions in stars allow highly excited states to be populated for which data is needed. Some new presumptive interstellar lines are reported. Title: Ultraviolet Spectroscopy of Cool Stars from IUE (invited Paper) Authors: Jordan, C.; Judge, P.; Johansson, S. Bibcode: 1984uxsa.coll...51J Altcode: 1984IAUCo..86...51J; 1984uxsa.conf...51J No abstract at ADS Title: A comparison between the observed and predicted Fe II spectrum in different plasmas. Authors: Johansson, S. Bibcode: 1984PhST....8...63J Altcode: 1984PhyS....8...63J This paper gives a survey of the spectral distribution of emission lines of Fe II, predicted from a single atomic model. The observed differences between the recorded and the predicted spectrum are discussed in terms of deficiencies of the model and interactions within the emitting plasma. The author gives a number of illustrative examples of unexpected features with applications to astrophysics. Title: Strong Fe II fluorescence lines in RR Tel and V1016 Cyg excited by C IV in a Bowen mechanism. Authors: Johansson, S. Bibcode: 1983MNRAS.205P..71J Altcode: Ten strong lines in the IUE spectrum of RR Tel have been identified as transitions from a common upper level of Fe II, y4H011/2. The level is selectively populated through resonant photoexcitation from a4F9/2 by one of the resonance lines of C IV, λ1548.2 Å. Five of these lines appear also in the spectrum of V1016 Cyg. Title: Two CR II multiplets around 1430 A appearing in absorption in the spectrum of a solar active region Authors: Johansson, S. Bibcode: 1982MNRAS.201P..63J Altcode: In a current analysis of Cr II two new multiplets have been identified around 1430 Å. The identification of 27 lines establishes the new terms y 6F0 and y 6D0 of the 3d3 4s 4p configuration by their combinations with 3d4 4s a 6D. Most of the lines appear in absorption in the spectrum of a solar active region. Title: Atomic Spectroscopy for Astrophysical Applications Authors: Johansson, S. Bibcode: 1981SSRv...29..387J Altcode: The recent work in atomic spectroscopy at the Department of Physics, University of Lund, is briefly reviewed and some examples of application to astrophysics are presented. Title: Beam-foil lifetime measurements of some Fe II energy levels Authors: Johansson, S.; Litzen, U.; Lundin, L.; Mannervik, S. Bibcode: 1981PhyS...24...30J Altcode: The decay of 11 Fe II spectral lines in the region 2500-3200 A has been recorded with the beam-foil technique. The line-blending problem has been carefully studied, and the measurements have yielded lifetimes for 5 levels believed to be unaffected by blends. No previous lifetime measurements were reported for these levels. Title: New Spectroscopic Data for the Iron Group Elements Authors: Johansson, S. Bibcode: 1981LIACo..23..229J Altcode: 1981cpsu.conf..229J No abstract at ADS Title: Absorption lines in upsilon Sgr identified as high-level transitions of Fe II. Authors: Johansson, S. Bibcode: 1978MNRAS.184..593J Altcode: Summary. An analysis of the high configurations of Fe ii has led to the identification of some 100 absorption lines in the photographic infrared spectrum of V Sagittarii. Almost all these lines belong to the transition arrays 3d6 5s-3d6 5p, 3d6 5p-3d6 Sd, 3d6 Sp-3d6 6s and 3d64d-3d64f of Fe ii, where the lower levels have an excitation potential between 9.6 and 11.3 eV. Some of these high-level transitions are enhanced in the laboratory source because of accidental resonance charge-transfer. Title: The spectrum and term system of Fe II. Authors: Johansson, S. Bibcode: 1978PhyS...18..217J Altcode: The spectrum of singly ionized iron, Fe II, has been recorded in the wavelength regions 900-2200 Å and 4800-11200 Å by means of a pulsed hollow-cathode discharge. In the vacuum-ultraviolet region identifications are given for 1358 lines. The list for the region above 4800 Å contains 1564 observed lines, 1341 of which are identified. In the 2200-4800 Å range about 350 lines in the line list published by Dobbie in 1938 have been newly identified. On the basis of interferometric measurements made by G. Norlén of 350 lines a recalculation of the whole term system has been performed. Altogether 576 energy levels are now known in Fe II, some 250 of which are the results of the present analysis. The levels belong to the configurations (3d6)4s, 5s, 6s, 4p, 5p, 3d, 4d, 5d, 4f and (3d54s)4s, 5s, 4p, 4d and 3d54p2. Theoretical predictions of the structure of the (3d64p + 3d65p + 3d54s4p) complex by J. Sinzelle and J. F. Wyart are in good agreement with the observations. The ionization energy has been determined to 130 563 ± 10 cm-1. Title: New Fe II identifications in the infrared spectrum of Eta Carinae. Authors: Johansson, S. Bibcode: 1977MNRAS.178P..17J Altcode: Summary. An extended analysis of the Fe ii spectrum, based on new observations in the infrared, has led to the identification of about 50 lines in the infrared spectrum of Eta Carinae. More than half of the lines belong to the 3d6 5s-3d6 Sp transition array. Title: The Finnish-Swedish laser project Authors: Johansson, S.; Paunonen, M.; Sharma, A. Bibcode: 1975lti..proc..120J Altcode: The design and operation of a laser satellite rangefinder are described. The design parameters of the system are outlined, and directional calibration is discussed. The transmitter is based on a Pockels-cell Q-switched ruby-laser configuration with pulse slicing and amplification stages. The receiver consists of an astronomical telescope with a parabolic mirror and a photomultiplier installed at the prime focus. Timing is accomplished using a quartz clock system synchronized with the Universal Time Scale by a LORAN phase-locked frequency-comparison receiver. Title: Analysis of 4d-4f transitions in Fe II. Authors: Johansson, S.; Litzen, U. Bibcode: 1974PhyS...10..121J Altcode: The Fe II-spectrum emitted from a pulsed hollow cathode has been investigated in the region 4 800-11 500 Å. As a first result of the analysis 481 lines have been identified as belonging to the 3d6(5D)4d-3d6 (5D)4f transition array. The term structure shows good agreement with predictions by R. D. Cowan.