Energy levels of pentavalent uranium in lithium fluoride crystals

Optical absorption, emission and excitation experiments have been performed on X and γ-irradiated lithium fluoride crystals activated with uranium oxydes. Besides the numerous absorption lines due to presumed hexavalent uranium ions, several sets of seven energy levels have been clearly identified as being due to pentavalent uranium centers in non-cubic symmetry. The spin-orbit coupling constant of the 5f electron of U5+, the crystal-field parameters and the g-tensor of the fundamental level have been deduced from a fitting for the optical levels of one U5+ center in C4sub(v) symmetry. (author)