Ab initio calculations including relativistic effects in the Breit-Pauli R-matrix (BPRM) method are reported for fine structure energy levels and oscillator strengths upto n=10 and 0<=l<=9 for 15 Li-like ions: C IV, N V, O VI, F VII, Ne VIII, Na IX, Mg X, Al XI, Si XII, S XIV, Ar XVI, Ca XIII, Ti XX, Cr XXII, and Ni XXVI. About one hundred bound fine structure energy levels of total angular momenta, 1/2<=J<=17/2 of even and odd parities, total orbital angular momentum, 0<=L<=9 and spin multiplicity (2S+1)=2, 4 are obtained for each ion. The levels provide almost 900 allowed bound-bound transitions. The BPRM method enables consideration of large set of transitions with uniform accuracy compared to the best available theoretical methods. The CC eigenfunction expansion for each ion includes the lowest 17 fine structure energy levels of the core configurations ls^2^, ls2s, ls2p, ls3s, ls3p and ls3d. The calculated energies of the ions agree with the measured values to within 1% for most levels. The transition probabilities show good agreement with the best available calculated values. The results provide the largest sets of energy levels and transition rates for the ions and are expected to be useful in the analysis of X-ray and EUV spectra from astrophysical sources.
We have built a line list in the near-infrared J and H bands (1.00-1.34, 1.49--1.80 {mu}m) by gathering a series of laboratory and computed line lists. Oscillator strengths and damping constants were computed or obtained by fitting the solar spectrum. The line list presented in this paper is, to our knowledge, the most complete one now available and supersedes previous lists.
The weighted oscillator strengths (gf) and the lifetimes for Si VI presented in this work were carried out in a multiconfiguration Hartree-Fock relativistic (HFR) approach. In this calculation, the electrostatic parameters were optimized by a least squares procedure, in order to improve the adjustment to experimental energy levels. This method produces gf-values that are in better agreement with intensity observations and lifetime values that are closer to the experimental ones. In this work we presented all the experimentally known electric dipole Si VI spectral lines.
In this paper we report calculations for energy levels, radiative rates, and electron impact excitation rates for transitions in OVII. The GRASP (general-purpose relativistic atomic structure package) is adopted for calculating energy levels and radiative rates. For determining the collision strengths and subsequently the excitation rates, the Dirac atomic R-matrix code (DARC) and the flexible atomic code (FAC) are used. Oscillator strengths, radiative rates, and line strengths are reported for all E1, E2, M1, and M2 transitions among the lowest 49 levels of OVII. Collision strengths have been averaged over a Maxwellian velocity distribution, and the resulting effective collision strengths are reported over a wide temperature range below 2x10^6^K. Additionally, lifetimes are also listed for all levels.
Based on relativistic wave functions from multiconfiguration Dirac-Hartree-Fock and configuration interaction calculations, E1, M1, E2, M2 transition rates, weighted oscillator strengths, and lifetimes are evaluated for the states of the (1s^2^)2s^2^2p^4^,2s2p^5^, and 2p^6^ configurations in all oxygen-like ions between F II and Kr XXIX. Valence and core-valence correlation effects were accounted for through single-double multireference (SD-MR) expansions to increasing sets of active orbitals. Computed energies are compared with the NIST recommended values, generally differing by less than 600cm^-1^.
Fast-moving knots (FMK) in the Galactic supernova remnant Cassiopeia A consist mainly of metals and allow us to study element production in supernovae and to investigate shock physics in great detail. We discuss and suggest observations of a previously unexplored class of spectral lines, the metal recombination lines in optical and near-infrared bands, emitted by the cold ionized and cooling plasma in fast-moving knots.
Parameterization of level-resolved RR data fro SPEX
Short Name:
J/A+A/587/A84
Date:
21 Oct 2021
Publisher:
CDS
Description:
The level-resolved radiative recombination (RR) rate coefficients for H-like to Na-like ions from H (Z=1) up to and including Zn (Z=30) are studied here. For H-like ions, the quantum-mechanical exact photoionization cross sections for nonrelativistic hydrogenic systems are used to calculate the RR rate coefficients under the principle of detailed balance, while for He-like to Na-like ions, the archival data on ADAS are adopted. Parameterizations are made for the direct capture rates in a wide temperature range. The fitting accuracies are better than 5% for about 99% of the ~3x10^4^ levels considered here. The ~1% exceptions include levels from low-charged many-electron ions, and/or high-shell (n>~4) levels are less important in terms of interpreting X-ray emitting astrophysical plasmas. The RR data will be incorporated into the high-resolution spectral analysis package SPEX.
We report a comprehensive list of accurate Ritz wavelengths for parity-forbidden [Co II] and [V II] lines obtained from the analysis of energy levels measured in the laboratory with Fourier transform emission spectroscopy. Such lines, particularly those in the infrared, are in demand for the analysis of low-density astrophysical plasmas in and around objects such as planetary nebulae, star-forming regions, and active galactic nuclei. Transitions between all known metastable levels of Co II and V II are included in our analysis, producing wavelengths for 1477 [V II] lines and 782 [Co II] lines. Of these, 170 [V II] lines and 171 [Co II] lines arise from transitions with calculated transition probabilities greater than 1x10^-2^/s and upper level excitations of less than 5 eV, and thus are likely to be observed in astrophysical spectra.
Partition functions and dissociation equilibrium constants are presented for 291 diatomic molecules for temperatures in the range from near absolute zero to 10000K, thus providing data for many diatomic molecules of astrophysical interest at low temperature. The calculations are based on molecular spectroscopic data from the book of Huber and Herzberg with significant improvements from the literature, especially updated data for ground states of many of the most important molecules by Irikura. Dissociation energies are collated from compilations of experimental and theoretical values. Partition functions for 284 species of atoms for all elements from H to U are also presented based on data collected at NIST. The calculated data are expected to be useful for modelling a range of low density astrophysical environments, especially star-forming regions, protoplanetary disks, the interstellar medium, and planetary and cool stellar atmospheres. The input data, which will be made available electronically, also provides a possible foundation for future improvement by the community.
The authors calculated atomic partition functions (APF) for iron ions, FeI-FeX, using recent compilations of atomic energy levels. Observed sets of atomic energy levels were filled through levels predicted in quantum mechanics and autoionization levels. Therefore, our APFs include levels above those tabulated. APFs are functions of temperature T and the lowering of ionisation energy (LIE). LIE is the result of emitter-plasma interactions in gas that cause dissolution of the highest energy levels and is applied here in a cut-off approximation.
