The effect of atomic rearrangement on the photoionisation cross section for 3d subshells of the isoelectronic Xe series

Abstract

The photoionisation cross sections for 3d10 subshells are calculated for the elements of the isoelectronic series of atomic Xe such as I-, Xe, Cs+, Ba2+ and La3+. The non-relativistic random-phase approximation with exchange (RPAE) is used to account for the static rearrangement. The maxima in Xe and I- spectra are due to the 3d- epsilon f transition into the continuum, and those for Ba2+ and La3+ are due to 3d-4f transitions to discrete levels. The photoabsorption cross section for Cs+ appears to be sensitive to the method of calculation; RPAE leads to maxima in the discrete spectrum, whereas the static rearrangement leads to a maximum in the continuum. Allowance for the rearrangement due to a 3d-vacancy decay lowers the cross section in the continuum, shifting the oscillator strengths to the discrete spectrum which reveals the existence of the so-called 'collapse' of the 4f electron.