6d15f1 ↔ 5f2 transitions in U4+ in Cs2NaYCl6

The paper presents absorption, emission and excitation spectra as well kinetics of U4+ embedded in Cs2NaYCl6. High hydrostatic pressure is also used to analyze the photoluminescence properties. Under excitation with 325 nm one observes three luminescence bands peaked at 370 nm, 420 nm and 520 nm, attributed to 6d1(t2g)5f1 → 5f2 transitions in U4+. All luminescence bands are characterized by single exponential decay equal to 6.1 ± 0.3 ns at room temperature and 22. ± 1 ns at 80 K. The luminescence excitation spectrum consists of four bands peaked at 338 nm, 320 nm, 305 nm and 280 nm, attributed to the spin allowed transitions from the ground state, 3H4 to the lowest triplets of the 6d1(t2g)5f1 electronic configuration. The pressure red shifts equal approximately to 23 ± 2.5 cm−1/kbar have been observed for all luminescence bands.