The primary processes occurring in the photolysis of SOCl, 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(D3rI4-X 3 C -) and SO(E311+ X3C-). 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.OfO.l eV. Molecular constants for the two states are given as
SO(D311)The extinction coefficient of the (7,O) band for the transition SO(B3C-+X3C-) is determined asThe kinetics of the reactions involving both the ground states and electronically excited states of 0 2 , 1 and S2,2 have received considerable attention; however, by comparison, quantitative data on the kinetics of the SO radical is more limited. This radical has been observed directly in a number of systems and by various techniques : Carrington et aL3 have reported observations on the e.p.r. spectrum of both ground state and the first singlet state of the SO radical, attributing its production to the energy transfer reaction, (1) Colin has observed the second singlet state in emission via the transition SO(blC+-+ X3C-). However, little has been reported on the kinetics of these two excited states. Norrish and Oldershaw have observed the SO(B3C-tX3C-) system in the ultraviolet using kinetic spectroscopy, following the flash photodissociation of SO, and SO,. The kinetics of SO in these systems are discussed ; however, it was not possible to derive quantitative kinetic data with their instrumentation. Thrush and Halstead have used flow tube techniques to follow the intensity of the SO, after glow and to monitor the rate of the termolecular recombination, Mass-spectrometric sampling techniques have also been employed to monitor the removal of SO following the reaction of oxygen atoms with carbonyl sulphideY7 and
The absolute rate for the addition of sulphur atoms S(33P~) to ethylene has been determined by means of kinetic spectroscopy in the vacuum ultra-violet. Further reaction of S ( 3 3 P ~) with the ethylene episulphide formed is extremely rapid and provides a mechanism for the catalyzed recombination of sulphur atoms under certain conditions, viz.,The rate constant for reaction (2) is determined as k2 = 1 . 2 f 0 . 1 5 ~ Further consideration is given to the primary step in the photolysis of CS2.cm3 molecule-' s-l.
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