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 spec troscopy was used to probe the vibrational and rotational state of the desorbed CO. The vibrational distribution of the CO is the same as th at determined under collision-free conditions in the gas phase. The ma jority of the desorbed molecules show far lower rotational temperature s 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 w ith the surface temperature, nor with a higher temperature caused by l ocal heating.