PHOTODISSOCIATION KINETICS OF C-N(+) CLUSTERS

The photodissociation dynamics of size-selected C-n(+) clusters with 1 9 less than or equal to n less than or equal to 29 is analysed using v isible and UV irradiation. Both the number of absorbed photons leading to dissociation, and the time decay of the associated internal energy state are determined. The measured dissociation time constants indica te an evaporative behaviour, where energy redistribution over the mode s of vibration occurs before dissociation. The RRKM theory is therefor e used and shown to lead to low dissociation energies. At the low leve ls of internal energy reached in our photodissociation experiments, a more appropriate model is proposed, which accounts for a restricted re distribution of energy inside the cluster. This model leads to dissoci ation energies ranging from 4.05 to 3.3 eV. One-photon dissociation is also observed with photon energies close to 4.5 eV. On the one hand, this suggests a dissociative process for this photo-excitation wavelen gth. On the other hand, it allows to get upper limits for the dissocia tion energies.