COMPARATIVE-STUDY OF SI-2P CORE-EXCITATION SPECTRA IN THE TETRAHEDRALMOLECULES SIX4 (WITH X=H, D, F, CL, BR, CH3)

High-resolution Si-2p photoabsorption spectra of SiX4 molecules (X = H , D, F, Cl, Br, CH3) are presented. High-resolution spectra were obtai ned for SiBr4 and Si(CH3)(4), and they are compared to the Si-2p spect ra of the other SiX4 molecules studied before. In all cases, vibration al fine structure of the Rydberg states could be resolved, allowing a derivation of vibrational energies and intramolecular distances of the core-excited molecules from Franck-Condon analyses. The results obtai ned for the various ligand atoms are compared with each other, and are discussed in the context of the equivalent-cores approximation. A det ailed analysis of the core-to-valence excitations in all SiX4 molecule s studied is also given. [S1050-2947(98)06001-6].