Influence of high pressure on emission spectra and crystal field strength for Eu³⁺ in GdOBr

The emission spectra of the Eu³⁺ ion in GdOBr:Eu³⁺ were measured in the range of pressure from 0 GPa to 12.4 GPa. The energy level schemes established from the spectra show that the splittings of the ⁷F₁, ⁷F₃ and ⁵D₁ multiplets decrease obviously with increasing pressure. The crystal-field parameters B_q^k and the crystal-field strength parameter S versus B_q^k were determined at different pressures. With pressurization S reduces and the J-mixings of the state functions for the Eu³⁺ ion decrease, which is in agreement with the decrease of the multiplet-splittings. This shows that for Eu³⁺ in REOX: Eu³⁺ the diminution of the crystal-field strength with pressure, the authenticity of which is under suspicion for several years, is certain.