Influence of High Pressure on Crystal Field Parameters for GdOBr:Er

The fluorescence spectra of GdOBr:Eu at room temperature and under high pressure up to 12 GPa were measured and analyzed. 43 lines were observed at ambient pressure in the wavenumber of 13 000～21 500 cm-1. From the fluorescence spectra, the major part of the 7F0～5 and all the 5D0~2 stark levels were determined. Under pressures, the 5D0~2 stark levels shift downwards, but the 7F0～5 stark levels shift upwards or downwards irregularly. The crystal field simulation calculation is conducted on the 49 7F states. The five nonzero crystal field parameters obtained at ambient pressure are as follows: B02=-1 124.0 cm-1, B04=-969.6 cm-1, B44=827.9 cm-1, B06=889.6 cm-1 and B46=377.0 cm-1. Under high pressures, B04 and B06 increase with pressure. While B46 decreases with pressure, B02 and B44 show somewhat irregular variations with perssure. From the crystal field parameters, crystal field strength S was deduced. At ambient pressure, S =445.0 cm-1. Under high pressures it decreases with pressure till about 8 GPa, then increases with pressure till 12 GPa.