Photodissociation of IF₂CCOF clusters by resonant IR radiation

Abstract

Results of studies on the dissociation of (IF₂CCOF) _n clusters upon resonant excitation of IF₂CCOF molecules by pulsed (~10^-7 s) IR laser radiation are reported. Two different channels of the cluster excitation, via vibrations of C–F (~9 μm) and C = O (~5.3 μm) 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 Φ _IR . A dissociation lag has been revealed; i.e. the dissociation of (IF₂CCOF) _n clusters has been found to occur only at values of Φ _IR that exceed a certain threshold value, Φ _IR  > Δ Φ _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 ~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.