- ID:
- ivo://CDS.VizieR/J/ApJ/855/21
- Title:
- Improved A^3^{Pi}-X^3^{Sigma}^-^ transitions of OH+
- Short Name:
- J/ApJ/855/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Molecular ions are key reaction intermediates in the interstellar medium. OH+ plays a central role in the formation of more complex chemical species and for estimating the cosmic ray ionization rate in astrophysical environments. Here, we use a recent analysis of a laboratory spectrum in conjunction with ab initio methods to calculate infrared and ultraviolet oscillator strengths. These new oscillator strengths include branch dependent intensity corrections, arising from the Herman-Wallis effect, that have not been included before. We estimate 10% total uncertainty in the UV and 6% total uncertainty in the IR for the oscillator strengths.
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- ID:
- ivo://CDS.VizieR/J/ApJS/211/5
- Title:
- Improved line data for the Swan system ^12^C^13^C
- Short Name:
- J/ApJS/211/5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new, accurate predictions for rotational line positions, excitation energies, and transition probabilities of the ^12^C^13^C isotopologue Swan d^3^{Pi}-a^3^{Pi} system 0-0, 0-1, 0-2, 1-0, 1-1, 1-2, 2-0, 2-1, and 2-2 vibrational bands. The line positions and energy levels were predicted through new analyses of published laboratory data for the ^12^C^13^C lines. Transition probabilities were derived from recent computations of transition dipole moments and related quantities. The ^12^C^13^C line data were combined with similar data for ^12^C_2_, reported in a companion paper (2013JQSRT.124...11B), and applied to produce synthetic spectra of carbon-rich metal-poor stars that have strong C_2_ Swan bands. The matches between synthesized and observed spectra were used to estimate band head positions for a few of the ^12^C^13^C vibrational bands and to verify that the new computed line data match observed spectra. The much weaker C_2_ lines of the bright red giant Arcturus were also synthesized in the band head regions.
- ID:
- ivo://CDS.VizieR/J/A+A/487/767
- Title:
- Improved predictions of nuclear reaction rates
- Short Name:
- J/A+A/487/767
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Nuclear reaction rates of astrophysical applications are traditionally determined on the basis of Hauser-Feshbach reaction codes. These codes adopt a number of approximations that have never been tested, such as a simplified width fluctuation correction, the neglect of delayed or multiple-particle emission during the electromagnetic decay cascade, or the absence of the pre-equilibrium contribution at increasing incident energies. The reaction code TALYS has been recently updated to estimate the Maxwellian-averaged reaction rates that are of astrophysical relevance. These new developments enable the reaction rates to be calculated with increased accuracy and reliability and the approximations of previous codes to be investigated.
- ID:
- ivo://CDS.VizieR/J/A+A/593/A27
- Title:
- Inelastic beryllium-hydrogen collision data
- Short Name:
- J/A+A/593/A27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Inelastic processes in low-energy Be+H and Be^+^+H^-^ collisions are treated for the states from the ground state up to the ionic state, with the aim to provide rate coefficients needed for non-LTE modeling of beryllium spectra in cool stellar atmospheres. The electronic molecular structure is determined by using a recently proposed model quantum approach that is based on an asymptotic method. Nonadiabatic nuclear dynamics is treated by means of multichannel formulas, based on the Landau-Zener model for nonadiabatic transition probabilities.
- ID:
- ivo://CDS.VizieR/J/ApJ/851/59
- Title:
- Inelastic calcium-hydrogen collision data
- Short Name:
- J/ApJ/851/59
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Inelastic cross sections and rate coefficients in Ca+H and Ca^+^+H^-^ collisions for all transitions between the 17 lowest covalent states plus one ionic molecular state are calculated based on the most recent ab initio adiabatic potentials for the 11 lowest molecular states, as well as on the model asymptotic potentials for higher-lying states, including the ground ionic molecular state. Nuclear dynamics is treated by the probability-current method and the multichannel formulas for the collision energy range 0.01-100eV. The rates are computed for mutual neutralization, ion-pair formation, and (de-)excitation processes for the temperature range T=1000-10000K. The calculations single out the partial processes with large and moderate rate coefficients. The largest rates correspond to the mutual neutralization into the Ca(4s5s^3^S), Ca(4s5p^3^P^0^), Ca(4s5s^1^S), and Ca(4s5p^1^P^0^) final states; at T=6000K the largest value is 5.50x10^-8^cm^3^/s for Ca(4s5s^3^S). Among the (de-)excitation processes, the largest rate coefficient corresponds to the Ca(4s5s^1^S)->Ca(4s5s^3^S) transition; at T=6000K, the largest rate has the value of 8.46x10^-9^cm^3^/s.
- ID:
- ivo://CDS.VizieR/J/A+A/587/A114
- Title:
- Inelastic calcium-hydrogen collision data
- Short Name:
- J/A+A/587/A114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Inelastic processes in low-energy Ca+H and Ca^+^+H^-^ collisions are treated for the states from the ground state up to the ionic state, in order to provide rate coefficients needed for non-LTE modeling of Ca in cool stellar atmospheres. Electronic molecular structure was determined using a recently proposed model approach based on an asymptotic method. Nonadiabatic nuclear dynamics are treated by means of multichannel formulas, based on the Landau-Zener model for nonadiabatic transition probabilities.
- ID:
- ivo://CDS.VizieR/J/A+A/606/A11
- Title:
- Inelastic e+Mg collision data
- Short Name:
- J/A+A/606/A11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results of calculations for inelastic e+Mg effective collision strengths for the lowest 25 physical states of MgI (up to 3s6p^1^P), and thus 300 transitions, from the convergent close-coupling (CCC) and the B-spline R-matrix (BSR) methods are presented. At temperatures of interest, ~5000K, the results of the two calculations differ on average by only 4%, with a scatter of 27%. As the methods are independent, this suggests that the calculations provide datasets for e+Mg collisions accurate to this level. Comparison with the commonly used dataset compiled by Mauas et al. (1988ApJ...330.1008M), covering 25 transitions among 12 states, suggests the Mauas et al. data are on average ~57% too low, and with a very large scatter of a factor of ~6.5. In particular the collision strength for the transition corresponding to the MgI intercombination line at 457nm is significantly underestimated by Mauas et al., which has consequences for models that employ this dataset. In giant stars the new data leads to a stronger line compared to previous non-LTE calculations, and thus a reduction in the non-LTE abundance correction by ~0.1dex (~25%). A non-LTE calculation in a supernova ejecta model shows this line becomes significantly stronger, by a factor of around two, alleviating the discrepancy where the 457nm line in typical models with Mg/O ratios close to solar tended to be too weak compared to observations.
- ID:
- ivo://CDS.VizieR/J/A+A/612/A90
- Title:
- Inelastic Fe+H collision data
- Short Name:
- J/A+A/612/A90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Data for inelastic processes due to hydrogen atom collisions with iron are needed for accurate modelling of the iron spectrum in late-type stars. Excitation and charge transfer in low-energy Fe+H collisions is studied theoretically using a previously presented method based on an asymptotic two-electron linear combination of atomic orbitals model of ionic-covalent interactions in the neutral atom-hydrogen-atom system, together with the multi-channel Landau-Zener model. An extensive calculation including 166 covalent states and 25 ionic states is presented and rate coefficients are calculated for temperatures in the range 1000-20000K. The largest rates are found for charge transfer processes to and from two clusters of states around 6.3 and 6.6eV excitation, corresponding in both cases to active 4d and 5p electrons undergoing transfer. Excitation and de-excitation processes among these two sets of states are also significant.
- ID:
- ivo://CDS.VizieR/J/A+A/618/A141
- Title:
- Inelastic H-atom collisions NLTE corrections
- Short Name:
- J/A+A/618/A141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Determination of high-precision abundances of late-type stars has been and always will be an important goal of spectroscopic studies, which requires accurate modeling of their stellar spectra with non-local thermodynamic equilibrium (NLTE) radiative transfer methods. This entails using up-to-date atomic data of the elements under study, which are still subject to large uncertainties. We investigate the role of hydrogen collisions in NLTE spectral line synthesis, and introduce a new general empirical recipe to determine inelastic charge transfer (CT) and bound-bound hydrogen collisional rates. This recipe is based on fitting the energy functional dependence of published quantum collisional rate coefficients of several neutral elements (BeI, NaI, MgI, AlI, SiI and CaI) using simple polynomial equations. We perform thorough NLTE abundance calculation tests using our method for four different atoms, Na, Mg, Al and Si, for a broad range of stellar parameters. We then compare the results to calculations computed using the published quantum rates for all the corresponding elements. We also compare to results computed using excitation collisional rates via the commonly used Drawin equation for different fudge factors, SH, applied. We demonstrate that our proposed method is able to reproduce the NLTE abundance corrections performed with the quantum rates for different spectral types and metallicities for representative NaI and AlI lines to within 0.05dex and 0.03dex, respectively. For MgI and SiI lines, the method performs better for the cool giants and dwarfs, while larger discrepancies up to 0.20dex could be obtained for some lines for the subgiants and warm dwarfs. We obtained larger NLTE correction differences between models incorporating Drawin rates relative to the quantum models by up to 0.40dex. These large discrepancies are potentially due to ignoring either or both CT and ionization collisional processes by hydrogen in our Drawin models.Our general empirical fitting method (EFM) for estimating hydrogen collision rates performs well in its ability to reproduce, within narrow uncertainties, the abundance corrections computed with models incorporating quantum collisional rates. It performs generally best for the cool and warm dwarfs, with slightly larger discrepancies obtained for the giants and subgiants. It could possibly be extended in the future to transitions of the same elements for which quantum calculations do not exist, or, in the absence of published quantum calculations, to other elements as well.
- ID:
- ivo://CDS.VizieR/J/A+A/608/A33
- Title:
- Inelastic manganese-hydrogen collisions data
- Short Name:
- J/A+A/608/A33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A simplified model is derived for estimating rate coefficients for inelastic processes in low-energy collisions of heavy particles with hydrogen, in particular, the rate coefficients with high and moderate values. Such processes are important for non-local thermodynamic equilibrium modeling of cool stellar atmospheres. The derived method is based on the asymptotic approach for electronic structure calculations and the Landau-Zener model for nonadiabatic transition probability determination. It is found that the rate coefficients are expressed via statistical probabilities and reduced rate coefficients. It is shown that the reduced rate coefficients for neutralization and ion-pair formation processes depend on single electronic bound energies of an atomic particle, while the reduced rate coefficients for excitation and de-excitation processes depend on two electronic bound energies. The reduced rate coefficients are calculated and tabulated as functions of electronic bound energies. The derived model is applied to barium-hydrogen ionic collisions. For the first time, rate coefficients are evaluated for inelastic processes in Ba^ + ^+H and Ba^2+^ + H^−^ collisions for all transitions between the states from the ground and up to and including the ionic state.
