Coexistence of Bound and Virtual-bound States in Shallow-core to Valence Spectroscopies

TL;DR

This paper develops a theoretical framework for understanding shallow-core to valence excitations, revealing a crossover from bound to virtual-bound states and explaining differences in transition types observed in x-ray scattering.

Contribution

It introduces a new theory for shallow-core to valence excitations when multiplet spread exceeds core-hole attraction, applicable to strongly correlated systems.

Findings

Identification of the crossover from bound to virtual-bound states

Explanation of differences between dipole and multipole transitions

Relevance to interpreting x-ray spectroscopies in complex materials

Abstract

We develop the theory for shallow-core to valence excitations when the multiplet spread is larger than the core-hole attraction, e.g., if the core and valence orbitals have the same principal quantum number. This results in a cross-over from bound to virtual-bound excited states with increasing energy and in large differences between dipole and high-order multipole transitions, as observed in inelastic x-ray scattering. The theory is important to obtain ground state information from x-ray spectroscopies of strongly correlated transition metal, rare-earth and actinide systems.