Energy levels of Pr3+: GdOCl under pressure

Excitation and luminescence spectra of Pr3+ in GdOCl were measured in the s pectral range from 11 000 cm(-1) to 22 500 cm(-1). At ambient pressure a to tal of 54 spectral lines were observed. Some of these lines cannot be expla ined by transitions between crystal-field levels of the regular Pr3+ sire i n 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 ener gy level scheme of the 4f(2) configuration could be derived. From the 34 le vels at ambient pressure. 31 could also be obtained under pressure. The ene rgy level scheme is described in terms of the free-ion parameters (F-k, alp ha, 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 pressur e were determined. Surprisingly, the crystal-field strength, calculated fro m the crystal-field parameters, first shows a slight decrease with increasi ng pressure.