title: Analyzing velocity map images to distinguish the primary methyl photofragments from those produced upon C-Cl bond photofission in chloroacetone at 193 nm.
abstract: We use a combination of crossed laser-molecular beam scattering experiments and velocity map imaging experiments to investigate the three primary photodissociation channels of chloroacetone at 193 nm: C-Cl bond photofission yielding CH(3)C(O)CH(2) radicals, C-C bond photofission yielding CH(3)CO and CH(2)Cl products, and C-CH(3) bond photofission resulting in CH(3) and C(O)CH(2)Cl products. Improved analysis of data previously reported by our group quantitatively identifies the contribution of this latter photodissociation channel. We introduce a forward convolution procedure to identify the portion of the signal, derived from the methyl image, which results from a two-step process in which C-Cl bond photofission is followed by the dissociation of the vibrationally excited CH(3)C(O)CH(2) radicals to CH(3) + COCH(2). Subtracting this from the total methyl signal identifies the methyl photofragments that result from the CH(3) + C(O)CH(2)Cl photofission channel. We find that about 89% of the chloroacetone molecules undergo C-Cl bond photofission to yield CH(3)C(O)CH(2) and Cl products; approximately 8% result in C-C bond photofission to yield CH(3)CO and CH(2)Cl products, and the remaining 2.6% undergo C-CH(3) bond photofission to yield CH(3) and C(O)CH(2)Cl products.
authors.affiliation: The James Franck Institute and Department of Chemistry, University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Bridget W
authors.initials: BW
authors.lastname: Alligood
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Straus
authors.forename: Laurie J
authors.initials: LJ
authors.lastname: Butler
mesh_terms: D000096:Acetone / Q000031:analogs & derivatives* / Q000737:chemistry*; D007834:Lasers; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry; D008956:Models, Chemical; D010777:Photochemistry; D011789:Quantum Theory; D014732:Vibration
chemical_list: D000096:Acetone; C051224:methyl radical; C006973:chloroacetone; D008697:Methane