Vacuum ultraviolet photoelectron spectroscopy of transient species. Part 3.—The SO(3Σ–) radical

Abstract

Sulphur monoxide (SO) has been produced in the gaseous phase by electrodeless discharge of sulphur dioxide + rare gas mixtures and by the reactions of atomic oxygen with carbon disulphide or hydrogen sulphide. The vacuum ultra-violet photoelectron spectrum of SO has been obtained using a He I 58.4 mm light source. Six ionisation potentials (i.p.) of SO(³Σ^–) have been determined. The values for the adiabatic i.p. values are 10.31, 13.50, ∼14.4, 14.94, 16.44 and ∼19.6 eV. CNDO calculations, including the effects of configuration interaction, have been made in order to identify the ionic states which have been formed. Four of the five bands show well-resolved vibrational fine structure which has been analysed in order to assist with identification of the ionic state formed. The first band also shows structure due to spin-orbit coupling. The relative intensities of the vibrational fine structures within a band have been compared with calculated Franck–Condon factors in order to estimate the bond lengths of the ion in its various states. These bond lengths and the measured vibrational level separations have been used with the known i.p. values of atomic sulphur and oxygen to construct a potential energy diagram for SO⁺.