The photolysis of 3-cyclopentenone adsorbed on an MgF2 surface

The photolysis of 3-cyclopentenone adsorbed on MgF2 at 193 nm has been investigated. B state resonance-enhanced multi-photon ionisation spectroscopy was used to probe the vibrational and rotational state of the desorbed CO. The vibrational distribution of the CO is the same as that determined under collision-free conditions in the gas phase. The majority of the desorbed molecules show far lower rotational temperatures and translational energies than are seen in the gas phase, but range up to the high values of 1700 K and 4000 cm−1 for CO(v = 0). These results demonstrate that the rotational mode is neither equilibrated with the surface temperature, nor with a higher temperature caused by local heating.