Investigation of O-X (X = Pyrrole or Pyridine) Cluster Photodissociation Near 226 nm.

We have recorded the O-atom velocity map photofragment ion images resulting from the photodissociation of O-pyrrole and O-pyridine clusters near 226 nm. To record the images, the O-atom photoproduct was state-selectively ionized and projected onto a two-dimensional (2D) position-sensitive detector. The resulting ion images from the clusters show evidence for three dissociation pathways. In the images from either cluster, we observe an isotropic process with kinetic energy near the one-photon limit, which is due to dissociation of the cluster into molecular subunits followed by secondary dissociation of molecular oxygen. Both O-pyrrole and O-pyridine also show a low kinetic energy process that appears to be isotropic in nature. This low kinetic energy process likely results from dissociation of the cluster resulting in significant internal energy in the organic fragment followed by secondary dissociation of O. Finally, our ion images for O-pyrrole show O atoms resulting from a two-photon dissociation channel, which has been previously attributed to the formation and subsequent photodissociation of excited O (a Δ). At similar laser intensities, O-pyridine does not show significant dissociation through the channel producing O (a Δ); however, this channel shows a laser intensity dependence for O-pyridine.