X-ray absorption via K  resonance complexes in oxygen ions

Abstract

The Kα resonance complexes in oxygen ions O i–O vi are theoretically computed, and resonance oscillator strengths and wavelengths are presented. The highly resolved photoionization cross-sections, with relativistic fine structure, are computed in the coupled channel approximation using the Breit–Pauli R-matrix method. A number of strong Kα resonances are found to be appreciable, with resonance oscillator strengths ƒr > 0.1. The Kα resonance wavelengths of O i–O vi lie in the relatively narrow wavelength range 22–23.5 Å, and the X-ray opacity in this region should therefore be significantly affected by K → L transitions in oxygen. The results should be useful in the interpretation of soft X-ray spectra observed from Chandra and XMM–Newton.