Photolysis of CH3SH and H2S at 243.1 nm studied by photofragment ion imaging

The near-UV photolyses of hydrogen sulfide and methanethiol following excitation at 243.1 nm have been investigated further using ion-imaging methods to monitor the nascent H atom photofragments. The angular distributions of these H atoms are found to be well described by anisotropy parameters, β=– 0.9 ± 0.2 (for CH3SH photolysis) and – 1.0 ± 0.2 (for H2S), consistent with the fact that the near-UV photodissociation of these parent molecules involves a perpendicular photoexcitation process followed by prompt S—H bond rupture. Analysis of the radial form of the ion images also serves to highlight the strong similarities between the primary photochemistry of these two thiols following excitation to their respective dissociative first excited singlet states and to confirm previous reports that the bulk of the excess energy in these two photodissociation processes appears in the form of product recoil.