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

Abstract The fluorescence spectra of the Eu 3+ ion in GdOBr:Eu 3+ were measured under pressures up to 12.4 GPa at room temperature. The dependence of the CF levels of the 5 D 0–2 and 7 F 0–4 multiplets for the Eu 3+ 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 7 F 1 , 7 F 3 and 5 D 1 multiplets decrease obviously. At higher pressure, the splittings of the 7 F 1 7F, and 5 D 1 multiplets increase slowly. On the basis of the experimental data, the free-ion parameters 7 F 1 and ζ the crystal-field parameters B 4 ζ and the crystal-field strength parameters S were determined at different pressures. The values of 7 F 1 and ζ always reduce with pressure. The central-field covalency mechanism is dominant for the reduction of F 2 and ζ.