title: Dynamics of acetone photooxidation on TiO2(110): state-resolved measurements of methyl photoproducts.
abstract: State-resolved laser techniques were used to study the internal state distributions of gas phase methyl radicals which are produced during the photooxidation of acetone on TiO2(110). This approach was used as a means of understanding the nature of the bimodal kinetic energy distributions for these radicals. Specifically, we investigated the population of the ν2 "umbrella mode" which has been shown to be important in similar photodissociation reactions where methyl radicals are liberated. We observed that for methyl radicals undergoing prompt dissociation (EK = 0.15 eV), the vibrational population in the umbrella mode is quite cold and can be characterized by a Tvib = 151 ± 15 K. Methyl radicals in this channel were also characterized by a rotational energy distribution of Trot = 325 ± 25 K which is comparable to the gas phase value obtained by acetone photolysis. State-resolved energy distributions also show that methyl radicals which are vibrationally excited have an overall kinetic energy distribution which is ~35 meV less than those which are in their vibrational ground state. This value is comparable to, but not exactly in agreement with, the known vibrational spacing of the ν2 mode and suggests that vibrationally excited methyl radicals have less energy available for translation.
authors.affiliation: Department of Chemistry, Stony Brook University, Stony Brook, New York 11794, USA.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Kershis
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Wilson
authors.forename: Michael G
authors.initials: MG
authors.lastname: White