CHARACTERIZATION OF THE ELECTRONIC-STRUCTURE OF SICL4 PROBED BY X-RAY-ABSORPTION AND ION DESORPTION TECHNIQUES

The high-resolution Si L(23)-edge X-ray absorption near-edge structure (XANES) total electron yield (TEY) spectrum and Cl+ photon-stimulated ion desorption (PSID) spectrum of condensed SiCl4 have been measured in the energy range 102-115 eV. The Cl+ PSID spectrum exhibits higher intensities than the TEY for the higher-energy peaks near 110 eV in th e XANES spectrum of condensed SiCl4. We assigned most of these higher- energy peaks to excitations of the Si 2p electron to Rydberg orbitals. The enhanced PSID intensities of Rydberg transitions originate from t he lower degree of coordination of surface molecules. The non-statisti cal branching ratio in the L(3)/L(2) intensity is explained by the pre sence of the exchange interaction between the core hole with the excit ed electron. Due to the reduced electron-core exchange energy in the s olid, the solid-bulk TEY and solid-surface Cl+ PSID spectra exhibit a larger L(3)/L(2) intensity ratio than the gas-phase absorption spectru m.