Effect of pressure on free-ion and crystal-field parameters of Pr3+ in LOCl (L = La, Pr, Gd)

Fluorescence and absorption spectra of Pr3+:PrOCl(PrPr) were measured in th e range from 11 500 cm(-1) to 22 500 cm(-1) under pressures up to 16 GPa. F rom these spectra, the pressure dependence of the energy-level scheme of th e 4f(2) configuration of Pr3+ could be partly derived. The effect of pressu re on the free-ion parameters F-2, F-4, F-6, and xi was determined and comp ared in detail with former results on Pr3+:LaOCl(PrLa) and Pr3+:GdOCl(PrGd) . The observed shifts can be described by a combination of central-field an d symmetry-restricted covalency in all cases. The variations of the crystal -field parameters are analyzed in the framework of the superposition model. Although specific features can be accounted for by this model, distinct de viations reveal the difficulties in applying this model to compounds with t wo different ligands.