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

Abstract

Predissociation in the $\tilde{A}^{2}A_{1}$ 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, $\nu_{3}. Ab initio$ 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 $CH_{3}O$ and $CF_{3}S$, where the C-X (X=O, S) bond breaking is again highly correlated with the extension of the C-X bond.