- ID:
- ivo://CDS.VizieR/J/A+A/606/A106
- Title:
- Inelastic manganese-hydrogen collisions data
- Short Name:
- J/A+A/606/A106
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The aim of this paper is to calculate cross sections and rate coefficients for inelastic processes in low-energy Mn+H and Mn^+^+H^-^ collisions, especially, for processes with high and moderate rate coefficients. These processes are required for non-local thermodynamic equilibrium (non-LTE) modeling of manganese spectra in cool stellar atmospheres, and in particular, for metal-poor stars. The calculations of the cross sections and the rate coefficients were performed by means of the quantum model approach within the framework of the Born-Oppenheimer formalism, that is, the asymptotic semi-empirical method for the electronic MnH molecular structure calculation followed by the nonadiabatic nuclear dynamical calculation by means of the multichannel analytic formulas. The cross sections and the rate coefficients for low-energy inelastic processes in manganese-hydrogen collisions are calculated for all transitions between 21 low-lying covalent states and one ionic state. We show that the highest values of the cross sections and the rate coefficients correspond to the mutual neutralization processes into the final atomic states Mn(3d^5^4s(^7^S)5s e ^6^S), Mn(3d^5^4s(^7^S)5p y ^8^P^o^), Mn(3d^5^4s(^7^S)5s e ^8^S), Mn(3d^5^4s(^7^S)4d e ^8^D) [the first group], the processes with the rate coefficients (at temperature T=6000K) of the values 4.38x10^-8^, 2.72x10^-8^, 1.98x10^-8^, and 1.59x10^-8^cm^3^/s, respectively, that is, with the rate coefficients exceeding 10^-8^cm^3^/s. The processes with moderate rate coefficients, that is, with values between 10^-10^ and 10^-8^cm^3^/s include many excitation, de-excitation, mutual neutralization and ion-pair formation processes. In addition to other processes involving the atomic states from the first group, the processes from the second group include those involving the following atomic states: Mn(3d^5^(^6^S)4s4p(^1^P^o^)y ^6^P^o^), Mn(3d^5^4s(^7^S)4de ^6^D), Mn(3d^5^4s(^7^S)5pw ^6^P^o^), Mn(3d^5^(^4^P)4s4p(^3^P^o^)y ^6^D^o^), Mn(3d^5^(^4^G)4s4p(^3^P^o^)y ^6^F^o^). The processes with the highest and moderate rate coefficients are expected to be important for non-LTE modeling of manganese spectra in stellar atmospheres.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/610/A57
- Title:
- Inelastic O+H collision data
- Short Name:
- J/A+A/610/A57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Excitation and charge transfer in low-energy O+H collisions is studied; it is a problem of importance for modelling stellar spectra and obtaining accurate oxygen abundances in late-type stars including the Sun. The collisions have been studied theoretically using a previously presented method based on an asymptotic two-electron linear combination of atomic orbitals (LCAO) model of ionic-covalent interactions in the neutral atom-hydrogen-atom system, together with the multichannel Landau-Zener model. The method has been extended to include configurations involving excited states of hydrogen using an estimate for the two-electron transition coupling, but this extension was found to not lead to any remarkably high rates. Rate coefficients are calculated for temperatures in the range 1000-20000K, and charge transfer and (de)excitation processes involving the first excited S-states, 4s.^5^S^o^ and 4s.^3^S^o^, are found to have the highest rates.
- ID:
- ivo://CDS.VizieR/J/A+A/572/A103
- Title:
- Inelastic silicon-hydrogen collision data
- Short Name:
- J/A+A/572/A103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Inelastic processes in low-energy Si+H and Si^+^+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 Si in cool stellar atmospheres. Electronic molecular structure is determined using a recently proposed model approach based on an asymptotic method in combination with available ab initio potentials. Nonadiabatic nuclear dynamics are treated by means of a combination of multichannel formulas and the branching-probability-current method, based on the Landau-Zener model for nonadiabatic transition probabilities.
- ID:
- ivo://CDS.VizieR/J/ApJS/95/535
- Title:
- Infrared CO line list for X 1{Sigma}+ state
- Short Name:
- J/ApJS/95/535
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A complete line list with improved accuracy for all the rotation- vibration transitions of the fundamental, first, and second overtone bands up to nu=20 and J=149 of the ground state X ^1^{Sigma}^+^ of the seven CO isotopes - 12C16O, 13C16O, 12C17O, 12C18O, 13C18O, 14C16O, and 13C17O - is made available to the astronomical community. A line list of the pure rotational transitions up to nu=5 and J=60 is also made available for these seven isotopes. This line list contains the transition frequency, the lower state energy, the Einstein A-value, the gf-value, the transition strength at 3000K or 1000K for the pure rotational transitions, the expectation value of the effective dipole moment operator, and the quantum numbers of each transition. Individual partition functions are reported in the temperature range of 500 to 10,000K.
- ID:
- ivo://CDS.VizieR/J/A+A/554/A24
- Title:
- Infra-red transitions of Ca and Mg
- Short Name:
- J/A+A/554/A24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- While solar spectra contain a lot of CaI and MgI infrared lines, no laboratory-measured spectra of these atoms have been reported for wavenumbers below 2000cm^-1^. This study reports CaI spectra in 1300-4500cm^-1^ range and MgI spectra in 1300-4500cm^-1^ range. We perform the time-resolved Fourier transform infrared spectroscopy study of a plasma created by the laser ablation of MgF_2_ and CaF_2_ targets in a vacuum. The oscillator strengths(f-values) are calculated using quantum defect theory (QDT) which shows good agreement with the available experimental and theoretical results. We report several CaI and MgI IR lines which have not been measured previously in laboratory. The recorded spectra allow to determine the excitation energies of some Ca I and Mg I states with high orbital momentum (l=4,5). We also provide a large list of QDT-calculated f-values for CaI and MgI in the range of 800-9000cm^-1^.
- ID:
- ivo://CDS.VizieR/J/A+A/319/720
- Title:
- Infrared transitions of SiO
- Short Name:
- J/A+A/319/720
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spectroscopic properties of SiO have been calculated from highly correlated wave functions. The computed dipole moments for v=0-3 agree well with the experimental data of Raymonda et al. (1970, J. Chem. Phys. 52, 3458). By comparing the present results with previous theoretical works, we estimate that the resulting line strengths should be the most accurate to date. The Einstein coefficients for the fundamental and the first overtone (v<=40, J<=100) are larger than the currently used values of Tipping & Chackerian (1981, J. Mol. Spectr. 88, 352), and should be tested in models of stellar atmospheres.
- ID:
- ivo://CDS.VizieR/J/ApJ/729/82
- Title:
- Integrated column densities vs shock age
- Short Name:
- J/ApJ/729/82
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- I present computations of the integrated column densities produced in the post-shock cooling layers and in the radiative precursors of partially cooled fast shocks as a function of the shock age. The results are applicable to the shock-heated warm/hot intergalactic medium which is expected to be a major baryonic reservoir and contain a large fraction of the so-called missing baryons. My computations indicate that readily observable amounts of intermediate and high ions, such as CIV, NV, and OVI, are created in the precursors of young shocks, for which the shocked gas remains hot and difficult to observe. I suggest that such precursors may provide a way to identify and estimate the "missing" baryonic mass associated with the shocks. The absorption-line signatures predicted here may be used to construct ion-ratio diagrams, which will serve as diagnostics for the photoionized gas in the precursors. In my numerical models, the time evolution of the shock structure, self-radiation, and associated metal-ion column densities are computed by a series of quasi-static models, each appropriate for a different shock age. The shock code used in this work calculates the non-equilibrium ionization and cooling, follows the radiative transfer of the shock self-radiation through the post-shock cooling layers, takes into account the resulting photoionization and heating rates, follows the dynamics of the cooling gas, and self-consistently computes the photoionization states in the precursor gas. I present a complete set of the age-dependent post-shock and precursor columns for all ionization states of the elements H, He, C, N, O, Ne, Mg, Si, S, and Fe as functions of the shock velocity, gas metallicity, and magnetic field.
- ID:
- ivo://CDS.VizieR/J/A+A/609/A22
- Title:
- Interstellar dust through the Fe K-edge
- Short Name:
- J/A+A/609/A22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The chemical and physical properties of interstellar dust in the densest regions of the Galaxy are still not well understood. X-rays provide a powerful probe since they can penetrate gas and dust over a wide range of column densities (up to 10^24^cm^-2^). The interaction (scattering and absorption) with the medium imprints spectral signatures that reflect the individual atoms which constitute the gas, molecule, or solid. In this work we investigate the ability of high resolution X-ray spectroscopy to probe the properties of cosmic grains containing iron. Although iron is heavily depleted into interstellar dust, the nature of the Fe-bearing grains is still largely uncertain. In our analysis we use iron K-edge synchrotron data of minerals likely present in the ISM dust taken at the European Synchrotron Radiation Facility. We explore the prospects of determining the chemical composition and the size of astrophysical dust in the Galactic centre and in molecular clouds with future X-ray missions. The energy resolution and the effective area of the present X-ray telescopes are not sufficient to detect and study the Fe K-edge, even for bright X-ray sources. From the analysis of the extinction cross sections of our dust models implemented in the spectral fitting program SPEX, the Fe K-edge is promising for investigating both the chemistry and the size distribution of the interstellar dust. We find that the chemical composition regulates the X-ray absorption fine structures in the post edge region, whereas the scattering feature in the pre-edge is sensitive to the mean grain size. Finally, we note that the Fe K-edge is insensitive to other dust properties, such as the porosity and the geometry of the dust.
- ID:
- ivo://CDS.VizieR/J/A+AS/103/57
- Title:
- Ion-atom collisions in Sun atmosphere
- Short Name:
- J/A+AS/103/57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/MNRAS/497/1443
- Title:
- Ionisation and ion fraction data
- Short Name:
- J/MNRAS/497/1443
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ion populations most frequently adopted for diagnostics in collisional plasmas are derived from the density independent, coronal approximation. In higher density, lower temperature conditions, ionisation rates are enhanced once metastable levels become populated, and recombination rates are suppressed if ions recombine into Rydberg levels. As a result, the formation temperatures of ions shift, altering the diagnostics of the plasma. To accurately model the effect of ionisation from metastable levels, new electron impact, ionisation cross sections have been calculated for oxygen, both for direct ionisation and excitation-auto-ionisation of the ground and metastable levels. The results have been incorporated into collisional radiative modelling to show how the ionisation equilibrium of oxygen changes once metastable levels become populated. Suppression of dielectronic recombination has been estimated and also included in the modelling, demonstrating the shifts with density in comparison to the coronal approximation. The final results for the ionisation equilibrium are used in differential emission measure modelling to predict line intensities for many lines emitted by OII-VI in the solar transition region. The predictions show improved agreement by 15-40% for OII, OVI and the inter-combination lines of OIII-V, when compared to results from coronal approximation modelling. While there are still discrepancies with observations of these lines, this could, to a large part, be explained by variability in the observations.
