Effect of pressure on electron state of Eu3+ in Gd2O2S

The fluorescence spectra of Eu3+ in Gd2O2S have been measured at room temperature and under pressures within the range of 0-14.8 GPa. The crystal-field levels of the 7F0-6 and 5D0-2 multiplets of the Eu3+ ion have been determined at different pressures. With increasing pressure the crystal-field splittings of the 7F2-5 and 5D2 multiplets increase; however, the splittings of 7F1 and 5D1 decrease. The crystal-field parameters Bqk and the crystal-field strength parameter St versus Bqk were also determined at different pressures. In the pressure range up to 14.8 GPa, St increases by 11%. Under pressure, the barycenters of the 7F1-2 and 5D0-2 multiplets descend, the Slater parameter F2 and the spin-orbit coupling parameter ζ reduce. The symmetry-restricted covalency mechanism plays a main role in the reduction of F2 and ζ. (orig.)