Optical spectroscopy and crystal-field analysis of U3+ : Ba2YCl7

Abstract

High resolution absorption spectra of a U³⁺(0.3%) : Ba₂YCl₇ single crystal were recorded in the 4000–50 000 cm⁻¹ range at 7 K. The observed crystal-field levels were assigned and fit to the parameters of the simplified angular overlap model (AOM) as well as a semi-empirical Hamiltonian representing the combined atomic and one-electron crystal-field interactions. The starting values of the AOM parameters were obtained from ab intio calculations. The analysis of the spectra allowed the assignment of 65 crystal-field levels with a relatively small rms deviation of 25 cm⁻¹ and has shown that the AOM approach can predict quite well the B^k_q crystal-field parameters. The value determined for the crystal-field strength parameter, N_v corresponds well with those determined for U³⁺ in other chloride single crystals.