Spectrum analysis of U3+-doped LaBr3 single crystals. Part 1: crystal-field analysis

Single crystals of U3+:LaBr3 were grown by the Bridgman–Stockbarger technique. High-resolution polarized absorption spectra of the crystals were recorded at 4.2 K in the 4000–50,000 cm−1 range. Sixty-four experimental crystal-field energy levels of the U3+ ion were fitted to a semiempirical Hamiltonian employing free-ion, one-electron crystal-field as well as two-particle correlation crystal-field (CCF) operators with an r.m.s. deviation of 28 cm−1. The performed analysis of the spectra enabled the determination of crystal-field parameters and assignment of the observed 5f3→5f3 transitions. The effects of selected CCF operators on the splitting of some specific U3+ multiplets have been investigated and the obtained values of Hamiltonian parameters are discussed and compared with those reported in previous analyses.