Ab initio study of the valence-electron relaxation effect on x-ray-emission spectra and the excitonic effect on electron-energy-loss spectra of the Si L2,3 edge

The valence-band-electron relaxation effect on x-ray-emission spectra and the excitonic effect on electron-energy-loss spectra of the Si L2,3 edge were studied using an ab initio self-consistent pseudo-atomic-orbital method with large unit cells. Comparisons of our theoretical results with experimental x-ray-emission and electron-energy-loss spectra of the Si L2,3 edge suggest that there is very little relaxation of valence-band electrons before the 2p core hole is filled by one of the valence electrons. When including the excitonic effect in electron-energy-loss near-edge-structure calculations, the valence band should therefore be kept the same as the ground state.