Theory of X-ray absorption and resonant X-ray emission spectra by electric quadrupole excitation in light rare-earth systems

We have made precise theoretical calculations for both 2p3/2→4f X-ray absorption spectroscopy (XAS) and 4d→2p3/2 resonant X-ray emission spectroscopy (RXES) by electric quadrupole excitations at the L3 edge of light rare-earth elements, by means of atomic model with full multiplet effects. The calculation is based on the second-order optical formula, and the effect of the incident photon polarization is taken into account. It is shown that the 4d–4f interaction plays a more important role in 4d→2p3/2 RXES than the 4f–4f interaction does. Moreover, the calculated results of 4d→2p3/2 RXES show the strong polarization dependence, and it is originated from the spin multiplicity, which is derived from the 4d–4f interaction, of the RXES final states.