			15min:

DEPENDENCE OF THE PHOTOFRAGMENTATION OF THE PERDEUTEROMETHOXY RADICAL ON THE C-O BOND EXTENSION.

BRIAN E. APPLEGATE, MICHAEL B. PUSHKARSKY AND TERRY A. MILLER, The Ohio State University, Dept. of Chemistry, Laser Spectroscopy Facility, 120 W. 18th Avenue, Columbus, Ohio 43210.

Predissociation in the \widetildeA²A₁ state of perdeuteromethoxy has been probed in a jet-cooled expansion by two techniques, fluorescence temporal decay and fluorescence depletion spectroscopy. The rate of photodissociation appears to not only be a function of total excitation energy but also of the vibrational mode excited. A threshold for the photodissociation is established at six quanta of the C-O stretch, ₃. Ab initio calculations of the bond length extension as a function of each vibrational mode of this radical allows us to compare the absolute bond extension to the rate of photofragmentation. This comparison establishes a clear threshold for C-O bond extension to achieve bond fission. Similar results have been obtained for clearly related radicals CH₃O and CF₃S, where the C-X (X=O, S) bond breaking is again highly correlated with the extension of the C-X bond.