Comparative study of Si-2p core-excitation spectra in the tetrahedral molecules 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 obtained for SiBr4 and Si(CH3)(4), and they are compared to the Si-2p spectra of the other SiX4 molecules studied before. In all cases, vibrational 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 obtained for the various ligand atoms are compared with each other, and are discussed in the context of the equivalent-cores approximation. A detailed analysis of the core-to-valence excitations in all SiX4 molecules studied is also given. [S1050-2947(98)06001-6].