A study of the threshold photoelectron spectra and the photoionisation yield curves of the silicon tetrahalides

Abstract

The threshold photoelectron spectra and the photoionisation yield curves of SiF 4, SiCl 4 and SiBr 4 have been recorded in the photon energy range 10–240 eV using synchrotron radiation. The outer valence shell photoelectron bands exhibit effects due to spin–orbit splitting and to Jahn–Teller interactions, and vibrational progressions associated with the Jahn–Teller active modes have been observed. The continuous nature of the inner valence shell photoelectron bands and the absence of main-lines demonstrates the importance of electron correlation in redistributing the intensity amongst satellite states. New Rydberg series have been observed in the photoionisation yield curves associated with excitation from the valence shell, and the improved resolution has allowed some earlier assignment discrepancies to be clarified. The threshold photoelectron spectra and ion yield curves recorded at higher energies display features attributable to the Si 2p,2s, Cl 2p and Br 3p shells. The photoelectron spectra have enabled the following splittings to be measured: Si 2p–2s, Si 2p 1/2–2p 3/2, Cl 2p 1/2–2p 3/2 and Br 3p 1/2–3p 3/2, and the corresponding values are 51.21, 0.52, 1.62 and 4.6 eV, respectively. The interpretation of the features observed in the SiBr 4 spectra has been based upon previously reported assignments of similar structure in SiF 4.