The unimolecular reaction of (CH3)3CNO following n−π* excitation with a tunable dye laser

The predissociation of (CH3)3CNO following the 570–710 nm laser excitation of the n-π* transition is reported. The small fluorescence quantum yield and its short lifetime (<20 ns) indicate efficient radiationless processes prior to dissociation. NO is the major dissociation product and its concentration was monitored in real time by using the two-photon laser excited fluorescence technique. The NO yield as a function of wavelength followed very closely the absorption contours of (CH3)3CNO. The NO production rate was ≳108 s−1 at all wavelengths studied and this rate is too fast to be consistent with a mechanism involving a radiationless transition to the ground electronic state followed by energy randomization and dissociation. Alternative predissociation mechanisms are considered.