X-ray absorption via K-alpha resonance complexes in oxygen ions

摘要

The K-alpha resonance complexes in oxygen ions O I - O VI are theoreticallycomputed and resonance oscillator strengths and wavelengths are presented. Thehighly resolved photoionization cross sections, with relativistic finestructure, are computed in the coupled channel approximation using theBreit-Pauli R-matrix method. A number of strong K-alpha resonances are found tobe appreciable, with resonance oscillator strengths f_r > 0.1. The K-alpharesonance wavelengths of O I-O VI lie in a relatively narrow wavelength range22 - 23.5 A, and the X-ray opacity in this region should therefore besignificantly affected by K --> L transitions in oxygen. The results should beuseful in the interpretation of soft X-ray spectra observed from Chandra andXMM-Newton.