Vibrational and ligand-field effects in the high resolution core-level spectroscopy of molecules

Abstract

High resolution Si2p and Br3d core-level spectra of small molecules (photoabsorption, photoelectron and Auger) all show fine structure due to vibrational or ligand field splitting. The Si2p photoelectron and photoabsorption spectra of SiH 4, SiD 4 and Si 2H 6 show rich vibrational structure from both the symmetric and the asymmetric SiH(D) vibrational modes. The symmetric ν 1 vibrational mode dominates the photoelectron spectra of SiH 4 ( ν 1 = 2379 cm −1) and SiD 4 ( ν 1 = 1710 cm −1). In contrast, the asymmetric bending mode is more dominant in the photoabsorption spectra of the early Rydberg levels of SiH 4 and SiD 4 and completely dominant in both the photoelectron and photoabsorption spectra of Si 2H 6. In contrast, the core-level spectra of heavy elements such as Br and I are dominated by ligand field splitting. The high resolution Br 3d photoelectron spectrum of HBr shows the 3 d 3 2 doublet and 3 d 5 2 triplet characteristic of ligand field splitting. This same splitting is shown to dominate the previously recorded MVV Auger spectrum and the pre-edge Br 3d photoabsorption spectrum.