R. Kisielius

Electron-Impact Excitation of O II Fine-Structure Levels

Effective collision strengths for forbidden transitions among the five energetically lowest fine-structure levels of O II are calculated in the Breit–Pauli approximation using the R-matrix method. Results are presented for the electron temperature range 100–100 000 K. The accuracy of the calculations is evaluated via the use of different types of radial orbital sets and a different configuration expansion basis for the target wavefunctions. A detailed assessment of previous available data is given, and erroneous results are highlighted. Our results reconfirm the validity of the original Seaton and Osterbrock scaling for the optical O II ratio, a matter of some recent controversy. Finally, we present plasma diagnostic diagrams using the best collision strengths and transition probabilities.

Calculation of photoionized plasmas with an average-atom model

We use a simple average-atom model (NIMP) to calculate the distribution of ionization in a photoionization-dominated plasma, for comparison with recent experimental measurements undertaken on the Z-machine at the Sandia National Laboratory. The agreement between theory and experiment is found to be as good for calculations with an average-atom model as for those generated by more detailed models.

Magnetic dipole transitions in 4d{sup N} configurations of tungsten ions

Magnetic dipole transitions between the levels of ground

Atomic Data for S II—Toward Better Diagnostics of Chemical Evolution in High-redshift Galaxies

4{d}^{N}

Stout: Cloudy's Atomic and Molecular Database

configurations of tungsten ions were analyzed by employing a large basis of interacting configurations. Previously introduced configuration interaction strength between two configurations was used to determine the configurations with the largest contribution to wave functions of atomic states for the considered configurations. Collisional-radiative modeling was performed for the levels of the ground configuration coupled through electric dipole transitions with

Theoretical energy level spectra and transition data for 4p64d2, 4p64d4f, and 4p54d3 configurations of W36+

4{p}^{5}4{d}^{N+1}

ATOMIC DATA FOR ZN II: IMPROVING SPECTRAL DIAGNOSTICS OF CHEMICAL EVOLUTION IN HIGH-REDSHIFT GALAXIES

and

Energy levels and radiative rates for transitions in Cr-like Co IV and Ni V

4{d}^{N\ensuremath{-}1}4f

Significance ofM2andE3transitions for4p54dN+1- and4p64dN−14f-configuration metastable-level lifetimes

configurations. New identification of some lines observed in the electron-beam ion trap plasma was proposed based on calculations in which wavelength convergence was reached.

Energy levels and transition probabilities for nitrogen-like Fe xx ,

Absorption-line spectroscopy is a powerful tool used to estimate element abundances in both the nearby and distant universe. The accuracy of the abundances thus derived is naturally limited by the accuracy of the atomic data assumed for the spectral lines. We have recently started a project to perform new extensive atomic data calculations used for optical/UV spectral lines in the plasma modeling code Cloudy using state of the art quantal calculations. Here, we demonstrate our approach by focussing on S II, an ion used to estimate metallicities for Milky Way interstellar clouds as well as distant damped Lyman-alpha (DLA) and sub-DLA absorber galaxies detected in the spectra of quasars and gamma-ray bursts. We report new extensive calculations of a large number of energy levels of S II, and the line strengths of the resulting radiative transitions. Our calculations are based on the configuration interaction approach within a numerical Hartree-Fock framework, and utilize both non-relativistic and quasirelativistic one-electron radial orbitals. The results of these new atomic calculations are then incorporated into Cloudy and applied to a lab plasma, and a typical DLA, for illustrative purposes. The new results imply relatively modest changes (0.04 dex) to the metallicities estimated from S II in past studies. These results will be readily applicable to other studies of S II in the Milky Way and other galaxies.