Author name code: hoangh-bin ADS astronomy entries on 2022-09-14 =author:"Hoang-Binh, D." ------------------------------------------------------------------------ Title: The ``on the energy shell'' simplification of the impulse approximation in Rydberg atom-neutral collisions Authors: Hoang-Binh, D.; van Regemorter, H. Bibcode: 1999AIPC..467..336H Altcode: 1999sls..conf..336H Three types of calculations are compared according to the approximations used for the (e+B) scattering amplitude fe(q-->q'): (i) Exact impulse approximation (without any further approximation); (ii) Impulse approximation+``on the energy shell'' approximation; (iii) Impulse approximation+``on the energy shell'' approximation+``scattering length'' approximation. Preliminary results have been obtained for Na(n,l)+Ar collisions, suggesting that the ``on the energy shell'' approximation breaks down for large momentum transfers Q. Title: On the shifts of magnesium Rydberg lines in the solar infrared spectrum. Authors: Hoang-Binh, D. Bibcode: 1994A&A...286..607H Altcode: New theoretical data for calculating the widths and shifts of solar high-l Rydberg lines of neutral magnesium are reported. The line shifts measured by Chang & Schoenfeld (1991) have been reanalysed to obtain mean values of the electron densities in the regions where the lines are formed. lt is found that, on the assumption that the shifts due to interaction with neutral hydrogen atoms are negligible, the lines are formed in a photospheric layer of about 200 km thick, at heights between 150 and 350 km, and electron densities between 1.5 10^12^ and 6.6 10^12^ cm^-3^. Title: On the Ion Broadening of the 12 MU M lines of Atomic Magnesium Authors: Hoang-Binh, D.; van Regemorter, H. Bibcode: 1994IAUS..154..353H Altcode: No abstract at ADS Title: New Atomic Data for MG I Lines Authors: Hoang-Binh, D. Bibcode: 1994IAUS..154..347H Altcode: No abstract at ADS Title: Stark broadening theory of solar Rydberg lines in the far-infrared spectrum Authors: van Regemorter, H.; Hoang-Binh, D. Bibcode: 1993A&A...277..623V Altcode: Line broadening theory is revisited to obtain simple formulae, in the specific case of isolated lines, resulting from transitions between nearly degenerate states of atomic magnesium. Both the widths and shifts, due to collisions with electrons and positive ions, are obtained without any elaborate calculations for all the Rydberg lines (n‧, l‧) → (n,l‧+1), (5≤n‧≤ 1O n‧≤n<11, l>3), listed by Jefferies (1991). Validity conditions of the formulae are given for all the transitions under study.

It is shown that inelastic weak collisions usually dominate the widths, and that adiabatic ion collisions always dominate the shifts and thus determine their signs. The shifts appear as good diagnostics; e.g. for the peculiar case of the 6h-7i line near 12 μm, good agreement with observations is obtained for electron and ion densities close to those in the line forming region. Title: Multiplet oscillator strengths for excited atomic magnesium Authors: Hoang-Binh, D. Bibcode: 1993A&AS...97..769H Altcode: Transitions between excited terms of the 1,3S, 1,3P0, 1,3D, 1,3F0, and 1,3G manyfolds of atomic magnesium have been calculated using the Coulomb approximation. The principal quantum numbers of the lower terms range from about 4 to 50. Title: On the formation of the solar emission lines near 12 microns Authors: Hoang-Binh, D. Bibcode: 1991A&A...241L..13H Altcode: An analysis of the populations of Rydberg states in the solar atmosphere is presented. In contrast to the calculations of Lemke and Holweger (1987) concerning Mg I, it is found that 7h is slightly overpopulated relative to 6g in the upper photosphere. This implies an enhancement of the stimulated emission in the 7h-6g line. The results are consistent with the observation of an emission core in the lines 7h-6g and 7i-6h of neutral magnesium (Brault and Noyes, 1983). Title: The level populations of hydrogen at high principal quantum numbers. Authors: Wilson, T. L.; Filges, L.; Hoang-Binh, D.; Stark, A. A. Bibcode: 1990A&A...238..331W Altcode: An empirical study of high lying level populations of atomic hydrogen, based on measurements of Delta-n = 1 transitions from the principal quantum numbers n = 90, 65 and 41 has been carried out for the H II region NGC 2024. A model for the electron density and temperature distributions of this source is presented. For the central 1.8 arcsec (FWHP) part of the source, the average value of the electron temperature is 7400 K + or - 500 K. The departure coefficients from the 'standard' theory (Brocklehurst 1970) fit better than the departure coefficients of Hoang-Binh (1983). The latter include a direct interaction between the populations and photons from the ionizing star of the high n levels (Lyman pumping). Reasons for the non-detection of Lyman pumping effects is NGC 2024 are discussed. Title: An exact calculation of hydrogenic radial integrals and oscillator strengths, for principal quantum numbers up to N equal to about 1000 Authors: Hoang-Binh, D. Bibcode: 1990A&A...238..449H Altcode: We present a simple method for calculating easily and accurately the Gordon formula. Exact values obtained for transitions between very high Rydberg states have allowed a check on the accuracy of approximate expressions derived from quasi-classical theory. The dependence of the dipole radial integral on angular momenta is investigated in detail. Simple formulae for the most important transitions in the Lyman, Balmer, Paschen, ... series are given. Title: The Broadening of Radio Recombination Lines by Ion Collisions: New Theoretical Results Authors: Hoang-Binh, D. Bibcode: 1990ASSL..163...51H Altcode: 1989rrl..conf...51H; 1990IAUCo.125...51H; 1990rrly.conf...51H No abstract at ADS Title: Ion-collision broadening of solar lines in the far-infrared and submillimeter spectrum Authors: Hoang-Binh, D.; Brault, P.; Picart, J.; Tran-Minh, N.; Vallee, O. Bibcode: 1987A&A...181..134H Altcode: The authors give new theoretical data for calculating the ion impact broadening of solar far-infrared and submillimeter lines. These are more accurate than, and should be preferred to data extrapolated directly from Griem's (1967) work on radio recombination lines. The variation of the line width as a function of the upper level of the transition has also been investigated. It may be a potentially important diagnostic tool for determining the physical conditions in the solar atmosphere. Title: Lyman line pumping and the modelling of H II regions Authors: Hoang-Binh, D. Bibcode: 1986A&A...156..393H Altcode: The author shows that Lyman line pumping (Hoang-Binh, 1983) reduces the maser action in radio recombination lines emitted by H II regions. This effect is equivalent to an increase of the electron density Ne without increasing the electron impact broadening. In the modelling of H II regions by means of radio line data, the variation of the parameter Ne could be significantly influenced by this pump mechanism. Title: Observations of radio recombination lines in the millimeter-wave spectrum of Orion A. Authors: Hoang-Binh, D.; Encrenaz, P.; Linke, R. A. Bibcode: 1985A&A...146L..19H Altcode: The authors have observed the H 42α, 40α, 39α, 52β, 57γ, and 60γ lines in the direction of the molecular cloud in Orion A. From the alpha line data, the derived values of the electron temperature, assuming local thermodynamic equilibrium (LTE), are close to 10000K, significantly higher than values ≅8500K, inferred from optical studies. The authors interpret this as an evidence for a significant deviation from LTE. This is confirmed by the analysis of the higher order lines, and is consistent with the recent results of Wilson and Pauls (1984). The importance of observations in the millimeter-wave spectrum is discussed. Title: On a cosmic alphabet. Authors: Hoang-Binh, D. Bibcode: 1985IAUS..112..493H Altcode: The choice of frequencies for SETI has been discussed by many authors. The author points out that the line spectrum provided by the hydrogen (H) atom is very rich, and covers a large spectral domain, from the ultraviolet to radio wavelengths. Since the H frequencies are universally known, a "cosmic alphabet" could be constructed with them. In a mono-frequency search for artificial radio signals, the frequency of the H166 alpha line, 1425 MHz, might be a good substitute for the frequency 1420 MHz of the H 21 cm line. In a multi-frequency search, the frequencies of the prominent Hn alpha lines near H 21 cm might be interesting. Title: Radiative excitation and the intensities of radio recombination lines. Authors: Hoang-Binh, D. Bibcode: 1983A&A...121L..19H Altcode: The present investigation of the influence of the absorption of stellar Lyman line photons on the population of highly excited states of H in H II regions indicates that, for hot ionizing stars with an effective temperature of more than 50,000 K, radiative excitation is unimportant. Radiative excitation is more efficient for cooler stars, of less than 40,000 K, and if the Lyman jump is sufficiently sharp, it may become an important process at stellar temperatures of less than 35,000 K. It is also found that, in nebulae excited by stars of spectral type later than about O6, the contribution of radiative excitation to radio recombination line intensities is not negligible. Title: On solar hydrogen lines in the far-infrared and submillimeter spectrum Authors: Hoang-Binh, D. Bibcode: 1982A&A...112L...3H Altcode: Strength of H n-alpha lines, where n ranges from 5 to 20 have been evaluated, using a recent model of the solar chromosphere. It is found that they are much stronger than coronal ions lines, formed by the process of dielectronic recombination; and their wavelength dependence is strongly affected by pressure broadening. Observation of these lines may provide useful diagnostics of the physical conditions in the chromosphere, as well as valuable information on the behavior of atoms in high Rydberg states. Title: The Frequency Dependence of the Carbon Recombination Line Authors: Hoang-Binh, D.; Walmsley, C. M. Bibcode: 1974A&A....35...49H Altcode: Summary. Current radio observations of the carbon line clouds are used to derive their physical parameters. b factors are calculated for a low temperature gas and the results are compared with those of previous authors. A comparison is then made of the line intensities observed as a function of frequency with those expected on the basis of simple theoretical models. It is found that for the thr&e most studied sources, the best fit to the observations is obtained if the emission is mainly due to spontaneous transitions. An electron density of 10 and a kinetic temperature of 100 K are the approximate parameters of the best fitting models. Key words: recombination line - H I cloud b factors Title: Physical parameters in carbon line regions Authors: Walmsley, M.; Hoang-Binh, D. Bibcode: 1974MmSAI..45..171W Altcode: The paper describes attempts to fit the frequency dependence of the carbon line strength from various regions for which a dilution correction to each observation was necessary because a simple point source model did not give a good fit for high frequency measurements. In one model, a considerable contribution to line strength comes from stimulation of the background continuum, giving a very steep dependence on frequency which is not observed. Fits may be obtained, however, for models in which the main contribution to the line strength comes from spontaneous emission. Title: Mean electron density of NGC 7027 inferred from H 85alpha line data. Authors: Hoang-Binh, D. Bibcode: 1972saim.conf..365H Altcode: No abstract at ADS Title: The broadening of radio recombination lines emitted by H II regions. Authors: Hoang-Binh, D. Bibcode: 1972saim.conf..367H Altcode: No abstract at ADS Title: Stark broadening and radio recombination lines in NGC 7027. Authors: Hoang-Binh, D. Bibcode: 1971A&A....10..159H Altcode: The observed upper limit for the ratio T /T0 of central H 109cc line to continuum brightness temperatures in NGC 7027 (Terzian and Balick, 1969) is shown to be consistent with an electron density Ne> 10 cm-8. The lower limit of 10 cm-8 for Ne is smaller by a factor 10 than that found by Goldberg (1970), who did not consider Stark broadening. Further, an emission measure considerably larger than the value derived by high frequency flux measurements is not found necessary to account for the upper limit for TL/To. Key words: Stark broadening - radio recombination lines - H II regions Title: On the Interpretation of Radio Recombination Lines Emitted by Galactic Nebulae Authors: Hoang-Binh, D. Bibcode: 1970ApL.....6..151H Altcode: No abstract at ADS Title: Influence of Dielectronic Recombination on the Radio Recombination Lines of Carbon Authors: Gayet, R.; Hoang Binh, D.; Joly, F.; McCarroll, R. Bibcode: 1969A&A.....1..365G Altcode: The influence of dielectronic recombination on the population of the highly excited states of carbon is examined under typical nebular conditions. The resuits indicate that in certain circumstances, dielectronic recombination can produce a considerable enhancement of the recombination lines. Thus, for example, in an H II region with an electron temperature 12000 K and electron density 50 cm-8, the C 109 line could appear in emission with an intensity of several per cent of that of the neighbouring H 109 o' line. However, there is not as yet sufficient information to permit the positive identification of the anomalous microwave line in NGC 2024 and IC 1795 as a carbon recombination line originating from an H II region. Title: Enhancement of the stimulated emission of radio-frequency lines of hydrogen Authors: Mac Caroll, R.; Hoang Binh, D. Bibcode: 1968AnAp...31..123M Altcode: No abstract at ADS Title: Radio Recombination Lines: Populations of Highly Excited States of Hydrogen Authors: Hoang-Binh, D. Bibcode: 1968ApL.....2..231H Altcode: No abstract at ADS