Energy levels of Pr3+: GdOCl under pressure

Excitation and luminescence spectra of Pr3+ in GdOCl were measured in the spectral range from 11 000 cm(-1) to 22 500 cm(-1). At ambient pressure a total of 54 spectral lines were observed. Some of these lines cannot be explained by transitions between crystal-field levels of the regular Pr3+ sire in GdOCl. Possible explanations of these lines are discussed. Under pressure up to 16 GPa, all lines exhibit a red-shift, from which a part of the energy level scheme of the 4f(2) configuration could be derived. From the 34 levels at ambient pressure. 31 could also be obtained under pressure. The energy level scheme is described in terms of the free-ion parameters (F-k, alpha, beta, gamma zeta, M-k, P-k) and crystal-held parameters (B-0(2), B-0(4), B-4(4), B-0(6), B-6(6)). The variations of these parameters under pressure were determined. Surprisingly, the crystal-field strength, calculated from the crystal-field parameters, first shows a slight decrease with increasing pressure.