Atomic Processes, Theories, and Data For X-Ray Astronomy
Department of Astronomy
The Ohio State University
Columbus, OH 43210
A review of theoretical approximations and experiments for
atomic data will be presented. The Close Coupling R-matrix method
affords an ab initio and self-consistent treatment of atomic
processes on a large-scale: electron impact excitation, photoionization,
electron-ion recombination (including both 'radiative' and 'dielectronic'
recombination), and transition probabilities. Agreement between
experiments and R-matrix results for electron-ion recombination
cross sections show that it is possible to calculate rates to
10-20% accuracy, and that there are no significant shortcomings.
However, comparison with the distorted wave method and its variants
is hampered by lack of availability of detailed cross sections,
transition probabilities, and rates for individual atomic transitions
over all temperature/density regimes of interest. Such a comparison
of fundamental atomic parameters is essential to not only benchmark
theories and experiments, but also to ascertain the validity
of neglecting or treating indirectly atomic effects such as resonances,
fine structure, plasma conditions, etc. Atomic database efforts,
including data computed but not yet publicly available, will
also be addressed.