THE NEAR-ULTRAVIOLET PHOTODISSOCIATION DYNAMICS OF AZOMETHANE

The photodissociation of azomethane following absorption of a single 3 51 nm photon was studied using the method of molecular beam photofragm ent translational spectroscopy. The dissociation was observed to proce ed via cleavage of both C-N bonds to yield N2 and two methyl radicals. The measured time-of-flight spectra show evidence that the two methyl radicals possess unequal velocities in the azomethane center of mass suggesting that the dissociation is not symmetric. The angles between the asymptotic center-of-mass velocities for all three fragments are s trongly correlated, implying that the methyldiazenyl radical (CH3N2) i ntermediate decomposes within a fraction of its rotational period. We conclude, therefore, that the dissociation is concerted, not stepwise as was inferred from recent time-resolved experiments. The overall tra nslational energy distributions for all the photofragments in the azom ethane center of mass reveal that an average of 60% of the total avail able energy appears as translation. A possible mechanism, consistent w ith the experimental findings, will be proposed and discussed.