Atomic Processes, Theories, and Data for X-Ray Astronomy

Details Atomic Processes, Theories, and Data for X-Ray Astronomy Atomic Processes, Theories, and Data for X-Ray Astronomy

Jun 2005

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005aipc..774..119p&link_type=abstract

X-RAY DIAGNOSTICS OF ASTROPHYSICAL PLASMAS: Theory, Experiment, and Observation. AIP Conference Proceedings, Volume 774, pp. 11

Computer Science

Databases

1

X-Ray Sources (Astronomical), Atomic Collisions, X-Ray Spectra, Astrophysical Plasma, Plasma Collision Processes, Electron Impact Excitation, X-Ray Sources, X-Ray Bursts, X-Ray, Atomic Processes And Interactions, Magnetohydrodynamics And Plasmas, Electron Collisions

Scientific paper

Physical processes underlying X-ray spectral formation may be influenced considerably by particle energy distribution in the source. It is found that different electron distributions - Maxwellian or Gaussian - in the plasma yield significantly different X-ray line ratios. Owing to energetically uneven occurrence of dense resonances in electron impact excitation cross sections for transitions in Fe XVII, line ratios with Maxwellian and Gaussian averaged rates may differ by up to a factor of two, thereby explaining outstanding discrepancies between two independent laboratory measurements using Electron-Beam-Ion-Traps, as well as with astrophysical observations. The Close Coupling R-matrix theory which includes resonances via an ab initio wavefunction expansion, vs. several variants of the Distorted Wave theory which does not, is discussed. The R-matrix method also enables a unified and self-consistent theoretical treatment of photoionization and (e + ion) recombination (inverse) processes, that includes both the radiative and dielectronic recombination and yields total and level-specific rate coefficients valid at all temperatures. Finally, atomic databases from the Opacity Project and Iron Project at the Center de Donnees Astronomiques de Strasbourg and the Ohio Supercomputer Center are described, including a novel on-line database to compute stellar opacities for an arbitrary mixture of elements.

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