Effect of pressure on the electron state of Eu3+ in GdOBr

The fluorescence spectra of the Eu(3+)ion in GdOBr:Eu3+ were measured under pressures up to 12.4 GPa at room temperature. The dependence of the CF levels of the D-5(0-2) and F-7(0-4) multiplets for the Eu3+ ion on pressure was obtained from the spectra. Below 8 Gpa with increasing pressure the splittings of the multiplets studied do not increase and that of the F-7(1), F-7(3) and D-5(1) multiplets decrease obviously. At higher pressure, the splittings of the F-7(1),F-7(3) and D-5(1) multiplets increase slowly. On the basis of the experimental data, the free-ion parameters F-2 and zeta, the crystal-field parameters B-q(k), and the crystal-field strength parameters S were determined at different pressures. The values of F-2 and zeta always reduce with pressure. The central-field covalency mechanism is dominant for the reduction of F-2 and zeta. (C) 1997 Elsevier Science S.A.