Photodissociation of Tetramethylene Sulfoxide at 193 and 248 nm in the Gas Phase

Article abstract of DOI:10.1021/j100048a012

The 193 and 248 nm photodissociation of tetramethylene sulfoxide (TMSO) in the gas phase has been investigated by using laser spectroscopic techniques.The vibrational state distributions of the nascent SO(X³Σ^-) photofragment following irradiation at 193 and 248 nm have been measured by using laser-induced fluorescence (LIF) spectroscopy on the B³Σ^- - X³Σ^- transition.These vibrational state distributions can be characterized as Boltzmann with vibrational temperatures of 1250 +/- 60 and 1220 +/- 60 K for the 193 and 248 nm photolyses, respectively.Assuming that the SO photofragment is produced in concert with a 1,4-tetramethylene diradical, the vibrational state distribution obtained in the 193 nm photolysis agrees well with an energy disposal model, in which the full reaction exoergicity is statistically partitioned among all the products' degrees of freedom.The quantum yield for SO(X³Σ^-) production at 193 nm, Φ¹⁹³_SO = 0.47 +/- 0.20, has been obtained by comparison with SO2 photolysis.For the 248 nm photodissociation, the experimentally obtained vibrational state distribution can be best described by a variant statistical model assuming three-body fragmentation; i.e. the products are an SO fragment and two ethylene molecules.The quantum yield for SO(X³Σ^-) production at 248 nm is Φ²⁴⁸_SO = 0.44 +/- 0.19.The OH photofragment has been detected during both the 193 and 248 nm photolyses of TMSO.The rotational state distributions of the OH(X²Π, ν'' = 0) fragment have been determined by LIF spectroscopy using the A²Σ-X²Π transition.The hydroxyl rotational temperatures can be characterized as 600 +/- 50 and 510 +/- 40 K following photolysis of TMSO at 193 and 248 nm, respectively.Mechanisms for the production of both SO and OH are discussed.