K-shell photoionization and electron impact excitation of Fe XVII–Fe XXIII^*

¹ Centro de Física, Instituto Venezolano de Investigaciones Científicas (IVIC), PO Box 21827, Caracas 1020A, Venezuela
² NASA Goddard Space Flight Center, Code 662, Greenbelt, MD 20771, USA

Corresponding author: M. A. Bautista, bautista@kant.ivic.ve

Received: 14 August 2003
Accepted: 30 October 2003

Abstract

Photoabsorption cross sections across the K edge of Fe xvii–Fe xxiii and electron impact K-shell excitation effective collision strengths in Fe xviii–Fe xxiii have been computed with the Breit-Pauli R-matrix method. The target models are represented with all the fine-structure levels within the  complex, built up from single-electron orbital bases obtained in a Thomas-Fermi-Dirac statistical model potential. The effects of radiation and spectator Auger dampings are taken into account by means of an optical potential. In photoabsorption, these effects cause the resonances converging to the K thresholds to display symmetric profiles of constant width that smear the edge, with important implications in spectral analysis. In collisional excitation, they attenuate resonances making their contributions to the effective collision strength practically negligible.