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-imagin g methods to monitor the nascent H atom photofragments. The angular di stributions of these H atoms ate found to be well described by anisotr opy parameters, beta = -0.9 +/- 0.2 (for CH3SH photolysis) and -1.0 +/ - 0.2 (for H2S), consistent with the fact that the near-UV photodissoc iation of these parent molecules involves a perpendicular photoexcitat ion process followed by prompt S-H bond rupture. Analysis of the radia l form of the ion images also serves to highlight the strong similarit ies between the primary photochemistry of these two thiols following e xcitation to their respective dissociative first excited singlet state s and to confirm previous reports that the bulk of the excess energy i n these two photodissociation processes appears in the form of product recoil.