VALENCE CORE EXCITED-STATES AND MULTIELECTRON EFFECTS IN THE PHOTOABSORPTION SPECTRUM OF SI(CH3)XCL4-X MOLECULES, NEAR THE SILICON AND CHLORINE-K EDGES

We report new photoabsorption spectra of chloro-methyl silane molecules (Si(CH3)xCl4-x, x = 0 to 4), measured near the silicon K (1800-2000 eV) and chlorine K (2810-2880 eV) edges. We observe significant variations on the energy and the number of valence core excited states with increasing methylation, because of the changes of the ligand electronegativity and of the symmetry group of the molecule. Multielectron effects of two different kinds are observed i) double-core-vacancy excited states of the Si K-1L-12,3 v* 2 type, in the EXAFS oscillations region ii) double core-valence-vacancy excited states of the Si K-1v-1v* 2 type right above the SiK ionization edge, overlapping partly with shape resonances. © 1990.