Photolysis of HCl in the Ar₂-HCl and Ar-HCl clusters: The cluster size effect

The photodissociation dynamics of HCl in the clusters Ar₂-HCl and Ar-HCl is studied in order to explore the cluster size effect. A quasiclassical trajectory approach is employed to simulate the photofragmentation dynamics. Interesting manifestations of the cage effect are found in the light and the heavy atom kinetic energy distributions, with important differences between the two clusters. The Ar and Cl distributions provide separate information on dynamical events which cannot be resolved in the hydrogen distribution. Only two different excitation wavelengths are used in the simulations. The cage effect is found to be strongly dependent on the wavelength employed to excite the HCl molecule. This is so to the extent that the trend of an increasing cage effect with the cluster size is reversed for the smaller wavelength. New types of resonance behavior are observed for the hydrogen motion in Ar₂-HCl compared with the Ar-HCl cluster. An interesting difference between Ar-HCl and Ar₂-HCl is that, in the latter case, Ar₂ can form as product of the photodissociation, with a high yield for the two wavelengths. The dynamics of the process and the implications of the results are discussed.