Photodissociation of IF2CCOF clusters by resonant IR radiation

Results of studies on the dissociation of (IF2CCOF)(n) clusters upon resonant excitation of IF2CCOF molecules by pulsed (similar to 10(-7) s) IR laser radiation are reported. Two different channels of the cluster excitation, via vibrations of C-F (similar to 9 mu m) and C=O (similar to 5.3 mu m) bonds in chromophore molecules, were used. It has been shown that, in both cases, the number of clusterized molecules decreases exponentially with increasing IR radiation fluence Phi(IR). A dissociation lag has been revealed; i.e. the dissociation of (IF2CCOF)(n) clusters has been found to occur only at values of Phi(IR) that exceed a certain threshold value, Phi(IR) > Delta Phi(th). The efficiency of cluster dissociation has been shown to depend only on the amount of absorbed energy and not to depend on the used channel of excitation. A phenomenological model of the cluster IR dissociation has been developed, which ensure a clear interpretation of experimental results. In particular, the energy required to evaporate the molecule and the mean size of the clusters under study have been estimated. It is concluded that, on a time scale similar to 10(-7) s, the process of the IR dissociation of (IF2CCOF)(n) clusters can be considered as a quasi-stationary process of successive evaporation of molecules in the course of cluster heating by resonant IR radiation.