Spectroscopic and kinetic studies of the SO radical and the photolysis of thionyl chloride

Abstract

The primary processes occurring in the photolysis of SOCl₂ have been examined using kinetic absorption spectroscopy in the ultra-violet and vacuum ultra-violet. Photodissociation involves the fission of one sulphur-chlorine bond, leaving an energized SOCl radical which may then undergo unimolecular decomposition to yield an SO radical and a further chlorine atom, or is stabilized by collision. The kinetics of the SO radical so formed are examined and a mechanism for removal is proposed. Two new electronic states of the SO radical are identified via new absorption systems in the vacuum ultra-violet designated SO(D³IIâ†�X³∑^–) and SO(E³IIâ†�X³∑^–). The D and E states are successive members of a Rydberg series and yield an approximate value for the first ionization potential of SO as 10.0 ± 0.1 eV. Molecular constants for the two states are given as [graphic omitted] The extinction coefficient of the (7,0) band for the transition SO(B³∑^–â†�X³∑^–) is determined as 8.0 ± 1.5 × 10⁶ cm² mol^–1.