DETERMINATION OF LOCAL DISTORTIONS AROUND SM2+ IN CAFCL FROM FLUORESCENCE STUDIES UNDER PRESSURE

The energy level scheme of Sm2+ in CaFCl is determined in detail from the fluorescence spectra of the D-5(j) --> F-7(j) transitions at ambie nt pressure and under pressures up to 8 GPa The crystal-held (CF) para meters B-q(k) are derived directly from CF energy levels and their var iations under pressure. The comparison of the CF interactions for Sm2 in different MFCl (M = Ba. Sr, and Ca) host crystals shows very simil ar behaviour under pressure. With the superposition model (SM), the lo cal structure around the Sm2+ ions in the CaFCl host is quantitatively determined and the four local structural parameters for the local coo rdination and the atom positions as well as their pressure dependences are derived. It is thus shown that the present method results in a va luable tool for the investigation of local distortions around opticall y active impurities.