STUDY OF THE TOTAL AND PARTIAL FRAGMENTATION DYNAMICS OF AR-HCL AFTERUV PHOTODISSOCIATION

The uv photolysis of the Ar-HCl cluster is studied applying an exact t ime-dependent wave packet method in three dimensions, assuming zero-to tal angular momentum. The photodissociation process is found to occur via two different fragmentation mechanisms, depending on the initial e xcitation energy of the cluster. One mechanism leads to total dissocia tion of the complex, producing three fragments, Ar-HCl+hv-->H+Ar+Cl. T he fragmentation dynamics in this case is governed by resonance states at relatively low energies of the cluster, in which the H atom collid es a number of times with Ar and Cl before dissociating. Manifestation s of these collisions are found in the final kinetic energy distributi on of the photofragments, which is redshifted in the case of the H fra gment, and blueshifted in the Ar and Cl cases. The second type of mech anism consists of a fast and direct photodissociation of the hydrogen, leading to a partial fragmentation of Ar-HCl into hot H fragments and bound Ar-Cl radical molecules. This mechanism dominates at higher ene rgies, which are those mostly populated by the wave packet initially p repared in the present calculations. The experimental implications of the results are discussed. (C) 1998 American Institute of Physics.