- ID:
- ivo://CDS.VizieR/J/A+A/460/959
- Title:
- Ni XIX radiative and excitation rates
- Short Name:
- J/A+A/460/959
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we report calculations for energy levels and radiative rates for transitions in Ni XIX. The General purpose Relativistic Atomic Structure Package (GRASP) has been adopted for the calculation of energy levels and radiative rates. Energies for the lowest 89 levels from the (1s^2^) 2s^2^2p^6^, 2s^2^2p^5^3l, 2s2p^6^3l, 2s^2^2p^5^4l and 2s2p^6^4l configurations of Ni XIX, are reported. Additionally, radiative rates, oscillator strengths, and line strengths are reported for all electric dipole (E1), magnetic dipole (M1), electric quadrupole (E2), and magnetic quadrupole (M2) transitions among these levels.
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- ID:
- ivo://CDS.VizieR/J/A+A/567/A18
- Title:
- Ni XV electron collisional excitation
- Short Name:
- J/A+A/567/A18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first R-matrix scattering calculation for electron collisional excitation of NiXV. The large-scale target includes configurations up to n=4. The calculations were carried out using the intermediate-coupling frame transformation method (ICFT). Significant enhancements in the collision strengths, compared to previous distorted wave (DW) calculations, are found for several cases, in particular the forbidden lines within the ground configuration and the 3s^2^ 3p 4s levels. We provide a complete set of rates and a list of strongest lines that are observable in astrophysical plasmas. Previous identifications are reviewed, and a few new ones suggested. The new data can be used to accurately measure electron densities for high-temperature (3MK) plasmas, and the nickel abundance.
- ID:
- ivo://CDS.VizieR/J/A+A/488/1155
- Title:
- Ni XXV energy levels and radiative rates
- Short Name:
- J/A+A/488/1155
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report calculations of energy levels and radiative rates for 1300 fine-structure levels generated from 189 configurations of Be-like Nickel. The General Purpose Relativistic Atomic Structure Program (GRASP2), developed by the I.P. Grant group in 1989 and partly improved by our group, is adopted in the calculations of energy levels and radiative rates. Our calculations are compared with those of other numerical methods and experiments so that their accuracy can be assessed. Additionally, the wavelengths, oscillator strengths, and radiative rates (for a given radiative rate and level structure, it is then easy to derive the line strength) a re reported for all electric dipole (E1), electric quadrupole (E2), magnetic dipole (M1) and magnetic quadrupole (M2) transitions among these levels. Finally, the lifetimes of all excited levels are reported.
- ID:
- ivo://CDS.VizieR/J/ApJS/185/477
- Title:
- N K-shell photoabsorption
- Short Name:
- J/ApJS/185/477
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Reliable atomic data have been computed for the spectral modeling of the nitrogen K lines, which may lead to useful astrophysical diagnostics. Data sets comprise valence and K-vacancy level energies, wavelengths, Einstein A-coefficients, radiative and Auger widths, and K-edge photoionization cross sections. An important issue is the lack of measurements that are usually employed to fine-tune calculations so as to attain spectroscopic accuracy. In order to estimate data quality, several atomic structure codes are used and extensive comparisons with previous theoretical data have been carried out. In the calculation of K photoabsorption with the Breit-Pauli R-matrix method, both radiation and Auger dampings, which cause the smearing of the K edge, are taken into account. This work is part of a wider project to compute atomic data in the X-ray regime to be included in the database of the popular xstar modeling code.
- ID:
- ivo://CDS.VizieR/J/A+A/385/716
- Title:
- N-like and O-like Breit-Pauli energy levels
- Short Name:
- J/A+A/385/716
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Breit-Pauli results for energy levels, lifetimes, and Lande g_J_ factors have been determined for all levels up to 2p^2^ 3d of the nitrogen-like sequence (Z=7-17) and 2p^3^ 3d of the oxygen-like sequence (Z=8-20). Exceptions are some lower members of the sequence where the spectrum included only those levels below the second 2p^2^ 4s term in the case of N-like or 2p^3^ 4s in the case of O-like. The computed energy and E1, E2, M1, M2 transition data between all levels, including convergence of the LS line strength for both length and velocity forms, may be viewed at a website, http://www.vuse.vanderbilt.edu/~cff/mchf_collection . In this paper, critically evaluated transition data is presented for NI, OII, MgVI, and SiVIII (N-like sequence) and OI, NeIII, MgV, and SiVII (O-like) for E1 transitions including uncertainty estimates. Tables 4 and 5 include the computed energy adjusted transition rates and uncertainty estimates as absolute values are calculated based on errors from energy adjustment and from LS convergence. The accuracy of energy levels is determined by comparison with experiment. Transition rates with uncertainties are compared with experiment and other theory.
- ID:
- ivo://CDS.VizieR/J/A+A/582/A61
- Title:
- N-like ions atomic data
- Short Name:
- J/A+A/582/A61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Extensive multiconfiguration Dirac-Hartree-Fock (MCDHF) calculations and relativistic configuration interaction (RCI) calculations are performed for 272 states of the 2s^2^2p^3^, 2s2p^4^, 2p^5^, 2s^2^2p^2^3l, 2s2p^3^3l, and 2p^4^3l (l = 0,1,2) configurations in the nitrogen-like ions Cr XVIII, Fe XX, Ni XXII, and Zn XXIV. Valence, core-valence, and core-core electron correlation effects are accounted for through large configuration state function expansions. Calculated energy levels are compared with data from other calculations and with experimental data from the NIST database. Lande gJ-factors; hyperfine structures; isotope shifts; and radiative electric dipole (E1), electric quadrupole (E2), and magnetic dipole (M1) transition rates are given for all ions. The accuracy of the calculated energy levels is high enough to facilitate identification of observed spectral lines involving the 2l^4^3l' configurations, for which experimental data are largely missing.
- ID:
- ivo://CDS.VizieR/J/A+A/546/A90
- Title:
- NLTE analysis of Sr lines
- Short Name:
- J/A+A/546/A90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the statistical equilibrium of neutral and singly-ionized strontium in late-type stellar atmospheres. Particular attention is given to the completeness of the model atom, which includes new energy levels, transition probabilities, photoionization and electron-impact excitation cross-sections computed with the R-matrix method. The NLTE model is applied to the analysis of SrI and SrII lines in the spectra of the Sun, Procyon, Arcturus, and HD 122563, showing a significant improvement in the ionization balance compared to LTE line formation calculations, which predict abundance discrepancies of up to 0.5dex. The solar Sr abundance is log(epsilon)=2.93+/-0.04dex, in agreement with the meteorites. We present the grid of NLTE abundance corrections for SrI and SrII lines that covers a wide range of stellar parameters. ************************************************************************** * * * The publication of the data will only be postponed until the * * accompanying paper is published * * * **************************************************************************
- ID:
- ivo://CDS.VizieR/J/MNRAS/418/863
- Title:
- NLTE corrections for Mg and Ca lines
- Short Name:
- J/MNRAS/418/863
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate NLTE effects for magnesium and calcium in the atmospheres of late-type giant and supergiant stars. The aim of this paper is to provide a grid of NLTE/LTE equivalent width ratios W/W* of Mg and Ca lines for the following range of stellar parameters: Teff in [3500,5250]K, log(g) in [0.5,2.0]dex and [Fe/H] in [-4.0,0.5]dex. We use realistic model atoms with the best physics available and taking into account the fine structure. The Mg and Ca lines of interest are in optical and near IR ranges. A special interest concerns the lines in the Gaia spectrograph (RVS) wavelength domain [847,874]nm. The NLTE corrections are provided as function of stellar parameters in an electronic table as well as in a polynomial form for the Gaia/RVS lines.
- ID:
- ivo://CDS.VizieR/J/A+A/555/A109
- Title:
- ^14^N/^15^N isotopic ratio in L1544
- Short Name:
- J/A+A/555/A109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Samples of pristine solar system material found in meteorites and interplanetary dust particles are highly enriched in ^15^N. Conspicuous nitrogen isotopic anomalies have also been measured in comets, and the ^14^N/^15^N abundance ratio of the Earth is itself higher than the recognised presolar value by almost a factor of two. Ion/molecules, low-temperature chemical reactions in the proto-solar nebula have been repeatedly indicated as being responsible for these ^15^N-enhancements. We have searched for ^15^N variants of the N2H^+^ ion in L1544, a prototypical starless cloud core that is one of the best candidate sources for detection owing to its low central core temperature and high CO depletion. The goal is to evaluate accurate and reliable ^14^N/^15^N ratio values for this species in the interstellar gas. A deep integration of the ^15^NNH^+^(1-0) line at 90.4GHz was obtained with the IRAM 30m telescope. Non-LTE radiative transfer modelling was performed on the J=1-0 emissions of the parent and ^15^N-containing dyazenilium ions, using a Bonnor-Ebert sphere as a model for the source. A high-quality fit of the N2H^+^(1-0) hyperfine spectrum has allowed us to derive a revised value of the N2H+ column density in L1544. Analysis of the observed N^15^NH^+^ and ^15^NNH^+^ spectra yielded an abundance ratio N(N^15^NH^+^)/N(^15^NNH^+^)=1.1+/-0.3. The obtained ^14^N/^15^N isotopic ratio is ~1000+/-200, suggestive of a sizeable ^15^N depletion in this molecular ion. Such a result is not consistent with the prediction of the current nitrogen chemical models. Since chemical models predict high ^15^N fractionation of N_2_H^+^, we suggest that ^15^N^14^N, or ^15^N in some other molecular form, is preferentially depleted onto dust grains.
- ID:
- ivo://CDS.VizieR/J/ApJS/162/428
- Title:
- n-propanol transition frequencies
- Short Name:
- J/ApJS/162/428
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of our continuing spectroscopic program of measuring the rotational spectra of large gas-phase molecules that may exist in observable quantities in the interstellar medium, we have studied the millimeter- and submillimeter-wave spectrum of the alcohol n-propanol (n-CH_3_CH_2_CH_2_OH), a straight-chain molecule with one more carbon atom than ethanol, which has already been detected in hot molecular cores. Although the molecule is thought to exist in five different conformers, we have only studied what is most likely to be the Gauche-trans (Gt) conformer, and analyzed over 2800 lines through 375GHz in frequency.
