Photoabsorption and photoionization of the 1s2 ground state of He-like ions near 2s2p 1P1 autoionizing resonance

For He-like ions, photoabsorption and photoionization cross-sections of 1s(2) can differ in the resonance region due to possible resonance radiative decays. This difference increases along isoelectronic sequence. As an example, the 2s2p autoionizing state is considered for different atomic elements (Z = 16, 20, 26). For these elements, we use atomic data computed, without radiative damping, by the R-matrix Breit-Pauli code for 1s(2) and 1s2s photoionization processes, which are available on atomic data websites. Applying Davies and Seaton's (1969 J. Phys. B: At. Mol. Phys. 2 757) radiative damping theory, we insert the damping effect. Comparisons are made with similar data computed by another code, which uses Robicheaux et al's (1995 Phys. Rev. A 52 1319) damping theory, also available on an atomic code website. We also present a very simple approximation of Davies and Seaton's theory, and test it by comparisons of data computed with and without the approximation.