Dissociation of methanol and ethanol activated by a chemical reaction or by light

When energized sufficiently either vibrationally or electronically, ROH (where R is methyl or ethyl) can dissociate to form H atoms and RO radicals. We have determined the translational energy release (〈E_Tr〉 = 0.82E_av1) and angular distribution (β = -0.60 ± 0.03) from the laser induced fluorescence spectra of H atoms produced in the 193 nm photodissociation of CD₃OH. We have also determined that the quantum yield for producing H from CD₃OH is 0.86 ± 0.10. In contrast, the reaction of O(¹D) + CH₄ which produces vibrationally excited CH₃OH, has a quantum yield for producing H atoms of roughly 0.25 with only 22% of the available energy released as translation. We conclude that although the total available energy is the same in both cases, the dissociation of photoexcited methanol is prompt whereas the dissociation of chemically activated methanol shows some degree of internal vibrational equilibration.