Physics – Atomic Physics
Scientific paper
Nov 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005phdt.........9d&link_type=abstract
Ph.D dissertation, 2005. Section 0168, Part 0606 198 pages; United States -- Ohio: The Ohio State University; 2005. Publication
Physics
Atomic Physics
Stellar, Opacities, Radiative Accelerations
Scientific paper
The Atomic physics field has served astronomy for a long time and it has also been stimulated by it. Despite the maturity of the field, the new requirements for accuracy and completeness from astronomers demand more challenging calculations. Current problems require the relaxation of approximations and a detailed study of different effects like relativistic effects, radiation damping and target expansions. We carry out elaborate relativistic atomic calculations using the Breit-Pauli R-matrix method to generate radiative and collisional data for atoms and ions of astrophysical interest.
Electron impact excitation of He-like ions (N, O, Ne, Mg, Al, Si, S and Ca) have been calculated including relativistic effects, the levels up to the complex n = 4 and radiation damping. A detailed study of their effects is presented here and the comparison with previous works shows differences of up to 30% in the effective collision strength for the z-line. This line with 3 other transitions between the complexes n = 1 and n = 2 constitute an important tool for plasma diagnostics and such differences will have strong consequences in the analysis of X-Ray spectra of astronomical objects.
We present the relativistic calculation of Ka resonances for oxygen ions that are responsible for X-Ray absorption features observed in the spectrum of the Seyfert 1 galaxy MCG-6-30-15 and other AGNs. The resonance oscillator strengths have been computed from the photoionization cross sections and appear to be strong. Comparison with the recent experimental and theoretical study of Ka photoionization of O II shows good agreement. These data should allow a more complete analysis of X-Ray spectra from AGNs and refine the general picture of such complex objects.
We report the first large relativistic calculation of the photoionization cross section of Fe II. The detailed fine structure in the present work agrees well with the experimental results from Kjeldsen et al. (2002) and represents an improvement over the previous non-relativistic results based on the LS coupling approximation. As a complement to the X-Ray analysis of AGNs, these data should be useful to the theoretical template of Fe II emissions crucial in the analysis of the UV/O/IR counterpart of the spectrum. (Abstract shortened by UMI.)
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