THE ENERGY LEVELS OF URANIUM IONS DOPED INTO CALCIUM FLUORIDE

Abstract

Uranium ions in $CaF_{2}$ crystals have been studied extensively via electron paramagnetic resonance and optical spectroscopy. Various valencies and charge compensation mechanisms have been claimed. Ab initio spin-orbit configuration interaction calculations are performed on these systems. The primary properties of interest are the energy levels and magnetic moments. The $CaF_{2}$ host is modeled with a large finite cluster of ions which approximate the Madelung potential of the crystal lattice. Uranium is modeled with relativistic effective core potentials and Gaussian cc-p VDZ basis sets. As an indication of accuracy it is noted that the best calculations on the $U^{4+}$ free ion have a maximum relative error or 9.6\% when compared to the experimental spectrum of this $5f^{2}$ configuration.