Energy levels of Pr 3+ :GdOCl under pressure

Excitation and luminescence spectra of Pr 3+ 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 Pr 3+ site 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 , α, β, γ, ζ, M k , P k ) and crystal-field parameters ( B 2 0 , B 4 0 , B 4 4 , B 6 0 , 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.