THE PHOTOCHEMISTRY OF ETHYLENE EPISULFOXIDE

The photochemistry of ethylene episulfoxide, C2H4SO, has been investig ated for the first time by using time-resolved laser-induced fluoresce nce (LIF) spectroscopy to probe the SO(X(3) Sigma(-)) photofragment on the (B-3 Sigma(-)-X(3) Sigma(-)) transition. Photodissociation of C2H 4SO at 193 and 248 nm produces SO(v('') = 0-6) and SO(v('') = 0-5), re spectively. The vibrational state distributions of the SO photofragmen t are inverted with maxima at v('') = 1 in both cases. Franck-Condon a nd impulsive models have been used to fit the experimentally observed vibrational state distributions and the internal energy content of the nascent SO(X(3) Sigma(-)) photofragment. These models are unable to f it the experimental observations, when the other fragment is ground-st ate ethylene, but excellent agreement is obtained for the lowest energ y triplet state of C2H4 The time-dependent behavior of the SO(X(3) Sig ma(-)) LIF signal has been measured, indicating a second ground-state sulfur monoxide production pathway. The experimental SO(X(3) Sigma(-)) transients can be fit by a biexponential function. The slower product ion of SO(X(3) Sigma(-)) is believed to be due to relaxation of SO(a(1 ) Delta), which is also produced in the photodissociation of C2H4SO. Q uantum yields for the production of SO(X(3) Sigma(-)) and SO(a(1) Delt a), based on a kinetic analysis, are 0.25 +/- 0.04 and 0.41 +/- 0.06 f ollowing 193 nm irradiation of C2H4SO and 0.34 +/- 0.06 and 0.44 +/- 0 .08 for the 248 nm photolysis.