Si 1s−1, 2s−1 and 2p−1 lifetime broadening of SiX4 (X = F, Cl, Br, CH3) molecules: SiF4 anomalous behaviour reassessed

Abstract

The Si 1s⁻¹, Si 2s⁻¹, and Si 2p⁻¹ photoelectron spectra of the SiX₄ molecules with X = F, Cl, Br, CH₃ were measured. From these spectra the Si 1s⁻¹ and Si 2s⁻¹ lifetime broadenings were determined, revealing a significantly larger value for the Si 2s⁻¹ core hole of SiF₄ than for the same core hole of the other molecules of the sequence. This finding is in line with the results of the Si 2p⁻¹ core holes of a number of SiX₄ molecules, with an exceptionally large broadening for SiF₄. For the Si 2s⁻¹ core hole of SiF₄ the difference to the other SiX₄ molecules can be explained in terms of Interatomic Coulomb Decay (ICD)-like processes. For the Si 2p⁻¹ core hole of SiF₄ the estimated values for the sum of the Intraatomic Auger Electron Decay (IAED) and ICD-like processes are too small to explain the observed linewidth. However, the results of the given discussion render for SiF₄ significant contributions from Electron Transfer Mediated Decay (ETMD)-like processes at least plausible. On the grounds of our results, some more molecular systems in which similar processes can be observed are identified.