Ultraviolet (formula presented) emission and crystal field analysis for (formula presented) in (formula presented)

Luminescence is reported from the (formula presented) level of (formula presented) in the cubic elpasolite lattices (formula presented) and (formula presented) Altogether, with the use of ultraviolet laser excitation, 11 transitions from (formula presented) (formula presented) (at 40 668 (formula presented)) to lower term multiplets have been observed and assigned. Transitions are also reported from the (formula presented) (formula presented) level at 32 613 (formula presented). The absence of emission from (formula presented) (at 31 367 (formula presented)) under the experimental conditions is rationalized. Up-conversion to (formula presented) which is not due to two-photon absorption, is reported for (formula presented) under blue pulsed laser excitation. Trap emission from (formula presented) defect sites has been observed under ultraviolet excitation. A preliminary investigation has been made of the electronic absorption spectra of (formula presented) and 58 Kramers quartet and doublet levels have been assigned, with a further 18 levels uncertain. The energy-level fit to 58 levels with total degeneracy 180 has been performed with a mean deviation of 20.4 (formula presented), which is improved to 16.8 (formula presented) if an empirical correction to the diagonal reduced matrix element of (formula presented) for (formula presented)H(2) term is included. The average error is similar for the 18 uncertain levels (total degeneracy 52). A comparison is included with the energy-level parametrizations of other (formula presented) systems.