- ID:
- ivo://CDS.VizieR/J/A+A/606/A147
- Title:
- Heavy particle-hydrogen collisions
- Short Name:
- J/A+A/606/A147
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive a simplified model for estimating atomic data on inelastic processes in low-energy collisions of heavy-particles with hydrogen, in particular for the inelastic processes with high and moderate rate coefficients. It is known that these processes are important for non-LTE modeling of cool stellar atmospheres. Rate coefficients are evaluated using a derived method, which is a simplified version of a recently proposed approach based on the asymptotic method for electronic structure calculations and the Landau-Zener model for nonadiabatic transition probability determination. The rate coefficients are found to be expressed via statistical probabilities and reduced rate coefficients. It turns out that the reduced rate coefficients for mutual neutralization and ion-pair formation processes depend on single electronic bound energies of an atom, 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 potassium-hydrogen collisions. For the first time, rate coefficients are evaluated for inelastic processes in K+H and K^+^ + H^-^ collisions for all transitions from ground states up to and including ionic states.
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- ID:
- ivo://CDS.VizieR/J/A+A/561/A135
- Title:
- HeI lines Stark broadening
- Short Name:
- J/A+A/561/A135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Stark broadening of the spectral lines of the wavelengths 501.6, 667.8, 728.1, 388.9, 587.6, and 706.5nm from neutral helium in plasmas are studied theoretically and experimentally. The aim of this work is to provide information about the connection between the shape and width of spectral lines and the electron density and temperature to be used as a diagnostic tool. The theoretical calculations were carried out through molecular dynamics computer simulations with noninteracting particles. The experimental measurements were done in a plasma of pure helium generated in an electromagnetically driven T-tube. The plasma diagnostics used previous results about the Stark broadening of the HeI 447.1nm and HeI 492.2nm lines and the coherence between the shape of these spectra and those obtained here. The electron temperature was obtained through a Boltzmann-plot of eight lines of SiII.
- ID:
- ivo://CDS.VizieR/J/A+A/566/L8
- Title:
- He IR absorption profiles
- Short Name:
- J/A+A/566/L8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Hydrogen-deficient white dwarfs are characterized by very dense, fluid-like atmospheres of complex physics and chemistry that are still poorly understood. The incomplete description of these atmospheres by the models results in serious problems with the description of spectra of these stars and subsequent difficulties in derivation of their surface parameters. Here, we address the problem of infrared (IR) opacities in the atmospheres of cool white dwarfs by direct ab initio simulations of IR absorption of dense helium. We applied state-of-the-art density functional theory-based quantum molecular dynamics simulations to obtain the time evolution of the induced dipole moment. The IR absorption coefficients were obtained by the Fourier transform of the dipole moment time autocorrelation function.
- ID:
- ivo://CDS.VizieR/J/A+A/600/A85
- Title:
- He-like ions (Z=20-42) effective collision strengths
- Short Name:
- J/A+A/600/A85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spectral lines of He-like ions are among the most prominent features in X-ray spectra from a large variety of astrophysical and high-temperature fusion plasmas. A reliable plasma modeling and interpretation of the spectra require a large amount of accurate atomic data related to various physical processes. In this paper, we focus on the electron-impact excitation (EIE) process. We adopted the independent process and isolated resonances approximation using distorted waves (IPIRDW). Resonant stabilizing transitions and decays to lower-lying autoionizing levels from the resonances are included as radiative damping. To verify the applicability of the IPIRDW approximation, an independent Dirac R-matrix calculation was also performed. The two sets of results show excellent agreement. We report electron impact excitation collision strengths for transitions among the lowest 49 levels of the 1snl(n<=5,l<=(n-1)) configurations in He-like ions with 20<=Z<=42. The line ratios R and G are calculated for Fe XXV and Kr XXXV.
- ID:
- ivo://CDS.VizieR/J/A+A/592/A141
- Title:
- Helium-like ions with Z=10-36 transition rates
- Short Name:
- J/A+A/592/A141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Helium-like ions provide an important X-ray spectral diagnostics in astrophysical and high-temperature fusion plasmas. An interpretation of the observed spectra provides information on temperature, density, and chemical compositions of the plasma. Such an analysis requires information for a wide range of atomic parameters, including energy levels and transition rates. Our aim is to provide a set of accurate energy levels and transition rates for helium-like ions with Z=10-36. The second-order many-body perturbation theory (MBPT) was adopted in this paper. To support our MBPT results, we performed an independent calculation using the multiconfiguration Dirac-Hartree-Fock (MCDHF) method.
- ID:
- ivo://CDS.VizieR/J/A+A/622/A127
- Title:
- H2/HD molecular data for quasar spectra analysis
- Short Name:
- J/A+A/622/A127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Absorption lines of H_2_ and HD molecules observed at high redshift in the line of sight towards quasars are a test ground to search for variation of the proton-to-electron mass ratio {mu}. For this purpose results from astronomical observations are compared with a compilation of molecular data of the highest accuracy, obtained in laboratory studies as well as in first principles calculations. A comprehensive line list is compiled for H_2_ and HD absorption lines in the Lyman (B^1^{Sigma}^+^_u_-X^1^{Sigma}^+^_g_) and Werner (C^1^{Pi}_u_-X^1^{Sigma}^+^_g_) bands systems up to the Lyman cutoff at 912{AA}. Molecular parameters listed for each line i are the transition wavelength {lambda}_i_, the line oscillator strength f_i_, the radiative damping parameter of the excited state {Gamma}_{i}, and the sensitivity coefficient K_i_ for a variation of the proton-to-electron mass ratio. The transition wavelengths {lambda}_i_ for the H_2_ and HD molecules are determined by a variety of advanced high-precision spectroscopic experiments involving narrowband vacuum ultraviolet lasers, Fourier-transform spectrometers and synchrotron radiation sources. Results for the line oscillator strengths f_i_, damping parameters {Gamma}_i_ and sensitivity coefficients K_i_ are obtained in theoretical quantum chemical calculations. A new list of molecular data is compiled for future analyses of cold clouds of hydrogen absorbers, specifically for studies of {mu}-variation from quasar data. The list is applied in a refit of quasar absorption spectra of B0642-5038 and J1237+0647 yielding constraints on a variation of the proton-to-electron mass ratio {Delta}{mu}/{mu} consistent with previous analyses.
- ID:
- ivo://CDS.VizieR/J/A+A/647/A155
- Title:
- H2:H2 inelastic collisions rate coefficients
- Short Name:
- J/A+A/647/A155
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this work, we present a pruned set of state-to-state rate coefficients (STS rates) for inelastic H_2_:H_2_ collisions in the thermal range from 10 to 1000K. The set includes all relevant rates needed for diagnostics based on the simulation of quadrupole infrared spectra of H_2_. The reported set was obtained from a quantum scattering close-coupling calculation employing a recent version of the MOLSCAT code, a high-level potential energy surface, and rotational energies of the H_2_ molecules with spectroscopic accuracy. These improvements have led to a significant increase in the accuracy with respect to previous computational results. The accuracy of the present STS rates is tested against recently reported experimental rates. Most dominant rates agree with the experiment within a 2{sigma} uncertainty (2 to 6%). In addition to the tables given in the main text, three machine-readable tables are available at the CDS. These tables include all the relevant numerical results of the paper, namely, the excitation and de-excitation STS rates for H_2_:H_2_ inelastic collisions at selected temperatures between 10 and 1000 K, and their functional description for interpolation at any intermediate temperature.
- ID:
- ivo://CDS.VizieR/J/A+AS/135/359
- Title:
- HI and HeII fine structure components
- Short Name:
- J/A+AS/135/359
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Emissivities have been calculated for fine-structure components of selected UV and optical recombination lines of HI and HeII. Results are given for a range of electron temperatures and densities, and in Cases A and B of Baker & Menzel (1938ApJ....88...52B). Relative intensities, wavelengths and velocity shifts of the fine-structure components are tabulated. Applications to the spectra of gaseous nebulae are discussed. Depending on the temperature, density and Case, the centres of unresolved lines can shift by up to 0.9km/s for HI and 3.3km/s for HeII. A new calibration of the H{alpha}-NII method for determining electron temperatures is given.
- ID:
- ivo://CDS.VizieR/VI/130
- Title:
- High accuracy computed H2D+ line list - ST1
- Short Name:
- VI/130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A comprehensive, calculated line list of frequencies and transition probabilities for the singly deuterated isotopologue of H_3_^+^, H_2_D^+^, is presented. The line list, called ST1, contains over 22 million rotational-vibrational transitions occurring between more than 33 thousand energy levels; it covers frequencies up to 18500cm-1. All energy levels with rotational quantum number, J, up to 20 are considered, making the line list useful for temperatures up to at least 3000K. About 15% of these levels are fully identified with six rotational and vibrational quantum numbers. The list is calculated using a previously proposed, high accuracy, ab initio model and consistency checks are carried out to test and validate the results. These checks confirm the accuracy of the list. A temperature-dependent partition function, valid over a more extended temperature range than those previously published, and cooling function are presented.
- ID:
- ivo://CDS.VizieR/VI/119
- Title:
- High accuracy computed water line list - BT2
- Short Name:
- VI/119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A computed list of H2O infra-red transition frequencies and intensities is presented. The list, BT2 was produced using a discrete variable representation two-step approach for solving the rotation-vibration nuclear motions. It is the most complete water line list in existence, comprising over 500 million transitions (65% more than any other list) and is also the most accurate (over 90% of all experimental levels are within 0.3cm^-1^ of the BT2 values). Its accuracy has been confirmed by extensive testing against astronomical and laboratory data. The line list has been used to identify water lines in a variety of objects including: comets, sunspots, a brown dwarf and the nova-like object V838 Mon. Comparison of the observed intensities with those generated by BT2 enables physical values to be derived for these objects. The line list can also be used to provide an opacity for models of the atmospheres of M-dwarf stars and assign previously unknown water lines in laboratory spectra.
