H-atom high-n Rydberg time-of-flight spectroscopy of C–H bond fission in acrolein dissociated at 193 nm

The experiments presented in this work use H-atom high-n Rydberg time-of-flight spectroscopy to measure the H-atom velocity distribution from one- and multiple-photon dissociation processes in acrolein following excitation at 193 nm. The one-photon H-atom signal is dominated by primary C–H bond fission in acrolein. We compare some of the qualitative features of the recoil translational energy distribution for the observed H atoms with what would be expected based on theoretical results for aldehydic C–H bond fission on the ground and lowest singlet and triplet excited states and conclude that the dissociation cannot proceed through either of these paths. A possible dissociation mechanism is proposed to account for the observed P(ET) that is consistent with the observation of an isotropic dissociation. Finally, we report results on methyl vinyl ketone photodissociation which provide evidence that the primary C–H bond fission process in acrolein is fission of the aldehydic bond.