Vibrational mode and frequency dependence of the photofragmentation of the methoxy radical

The photodissociation process for the jet-cooled methoxy radical at energies above the origin of the à state has been probed by several techniques: laser induced fluorescence, fluorescence temporal decay, and fluorescence depletion spectroscopy. A threshold for this process is clearly established. Above that threshold the ratio for the competing processes of photon emission and bond fission vary strongly. This variation is a function not only of the total excitation energy but is also strongly mediated by the nature of the vibrational motion involved. It is found that excitation of the ν3 mode (or other components in Fermi resonance with it) strongly promotes the breaking of the C–O bond.