Analysis of absorption and luminescence spectra of U3+ doped Cs2NaYCl6 and Cs2LiYCl6 single crystals

Abstract

Uranium (3+) doped single crystals of Cs2NaYCl6 and Cs2LiYCl6 with a 2.0% and 0.1% U3+ concentration have been obtained by the Bridgman-Stockbarger method. Luminescence spectra of the crystals were recorded at 160, 70, and 15 K. The emission bands observed in the visible and near infrared regions have been assigned to transitions from the lowest components of the I11/24, F3/24, and G7/24 multiplets to the crystal-field components of the I9/24 ground level. Absorption spectra were recorded from 4 000 to 25 000 cm−1 at 4.2 K. The zero phonon transitions were identified from an analysis of the vibronic side bands as well as in least-squares fits by applying a semiempirical Hamiltonian representing the combined atomic and crystal-field interactions for an ion of the 5f3 configuration and Oh symmetry. Eight energy level parameters were varied simultaneously in the least-squares adjustments yielding a mean error of 57 and 61 cm−1 for U3+:Cs2LiYCl6 and U3+:Cs2NaYCl6, respectively. The analysis of the spectra enabled the assignment of 25 crystal field levels for U3+:Cs2NaYCl6 and 27 for U3+:Cs2LiYCl6. The received total splitting of the ground level is equal to 625 and 595 cm−1, respectively.