Laser Ionization Measurements of the Photodissociation Kinetics of Jet-Cooled Benzaldehyde

Abstract

The kinetics of benzaldehyde dissociation into benzene and carbon monoxide following excitation to the S2 state has been investigated under jet-cooled conditions by two-color laser ionization mass spectrometry using a pump−probe technique. A kinetic model has been proposed to explain the observed biexponential decay of the benzaldehyde signal and the single-exponential growth of the benzene product signal in terms of a sequential decay of two excited states of benzaldehyde, one of which leads to formation of benzene molecules in its lowest triplet state. Reactant disappearance and product appearance rates were determined for a number of vibronic transitions in the first 2000 cm-1 energy region of the S2 state. At the S2 origin the decay rate of the short-lived state of benzaldehyde was found to be 1.2 × 106 s-1.