OCCUPIED ELECTRONIC STATES OF CASI2 AND CASI - SOFT-X-RAY FLUORESCENCE SPECTROSCOPY

The CaL(2,3) and SiL(2,3) fluorescence spectra for CaSi2 and CaSi are studied. These spectra provide s and d partial density-of-states (PDOS ) information for the Ca and Si atoms. The measured PDOS's are in good agreement with available calculations. Using monochromatized x rays t o excite core electrons to localized Ca d states near threshold produc es resonant recombination fluorescence peaks for the L(3) and L(2) edg es of Ca in both compounds. In CaSi, with resonant excitation, inelast ic Raman peaks are also observed. The energy position of the inelastic peaks indicates that the creation of the core hole shifts the Ca d st ates by several eV. The intensity of the resonance peaks indicates the degree of localization of the Ca d states, which is reduced by their participation in the bonding of the silicides. The empty Ca d states a re found to be quite localized in CaSi, and less so in CaSi2.