State-selected imaging studies of formic acid photodissociation dynamics

The photodissociation dynamics of formic acid have been studied using the velocity map ion imaging at the UV region. The measurements were made with resonance enhancement multiphoton ionization (REMPI) spectroscopy and dc slicing ion imaging. The OH REMPI spectrum from the photodissociation of formic acid at 244 nm has been recorded. The spectrum shows low rotational excitation (N≤4). By fixing the probe laser at the specific rotational transitions, the resulting OH images from various dissociation wavelengths have been accumulated. The translational energy distributions derived from the OH images imply that about half of the available energies go to the photofragments internal excitation. The dissociation dynamics of formic acid were also discussed in view of the recent theoretical calculations.