Methylsulfonyl Radical Unimolecular Dissociation Studied by Deep-UV Ultrafast Photoionization Spectroscopy

Abstract

The secondary dissociation dynamics of the methylsulfonyl radical following the photodissociation near 193 nm of methylsulfonyl chloride and methylsulfonyl ethanol has been studied using femtosecond mass-resolved photoionization spectroscopy. The primary dissociation is instrument-limited (<200 fs) for both precursors. The methylsulfonyl unimolecular dissociation is measured to have a lifetime of 0.34 ps with complete secondary dissociation following methylsulfonyl chloride photolysis. For the case of methylsulfonyl ethanol, the measured lifetime is 1.1 ps and ∼40% of the radical remains undissociated for the 18 ps duration of the experiment. We have successfully modeled the experimental results assuming an impulsive dissociation process to yield the internal energy distributions in the primary photoproducts and RRKM calculations based on structures and energetics of the methylsulfonyl radical obtained from the literature.