X-ray spectroscopy on the active ion in laser crystals

The active ions in typical laser crystals were studied with Resonant Inelastic X-ray Scattering (RIXS) and Partial Fluorescence Yield X-ray Absorption (PFY-XAS) spectroscopies as solid state model systems for dilute active centers. We analyzed Ti³⁺ and Cr³⁺ in α-Al₂O₃:Ti³⁺ and LiCaAlF₆:Cr³⁺, respectively. The comparison of experimental data with semi-empirical multiplet calculations provides insights into the electronic structure and shows how measured crystal field energies are related across different spectroscopies.