High Momentum Transfer Shallow Core-to-valence Spectroscopy in the Actinides

We calculate the dynamic structure factor S($q$,$\omega )$ within a renormalized atomic multiplet approach, to describe the 5d$\to $5f non-resonant inelastic x-ray scattering (NIXS) in actinide compounds ThO$_{2}$ (5f$^{0})$ and UO$_{2}$ (5f$^{2})$. For small $q,$ the spectra select the dipole-allowed transitions which are degenerate with continuum states, hindering their use in ground electronic structure determination. However dipole-forbidden multiplets reached with large $q$ are strongly bound to the core-hole, enabling the use of a renormalized atom approach to extract the ground state electronic structure. This crossover from unbound to bound states, reachable by low-$q$ and high-$q$ experiments respectively, is a result of the large multiplet spread of the 5d$^{9}$5f$^{N+1}$ multiplets exceeding the attractive core-hole potential. We discuss the details of the calculations and emphasize the importance of high-$q$ experiments in studies of the ground state electronic structure of actinides.