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The sequential photodissociation dynamics of (HI)2 is studied by means of a nonadiabatic wave packet treatment starting from the I*-HI complex. The model reproduces the main experimental findings for photolysis with 266 nm radiation. The results confirm that some of the H atoms dissociated from the I*-HI complex deactivate the I* atom through a H/I* intracluster collision which induces an I*→I electronically nonadiabatic transition. As a consequence, these H fragments become very fast by acquiring nearly all the I* excitation energy, equivalent to the I*/I spin-orbit splitting. A most interesting result is the high production of bound I2 fragments in highly excited rovibrational states in the photolysis, indicating that the H dissociation is mainly direct. [ABSTRACT FROM AUTHOR]

The Gaussian wave packet method has been developed for the simulation of processes like molecular collisions, photodissociation of molecules, and laser excitations of molecules. So far a necessary condition for an accurate result is that the fragment states are propagated accurately. We have considered one-dimensional bound states described by a Morse potential, and carried out a systematic study of the ability of the Gaussian wave packet method to propagate the stationary states. It is found that the complete set of equations of motion as derived by the minimum error method (MEM) cannot be used in practical calculations because of numerical problems. These are eliminated by the introduction of simplifications such as the independent Gaussian approximation (IGA), where each wave packet is propagated independently. The conditions for an accurate propagation within that assumption are developed, and a simple method is devised to identify those states, which are propagated accurately. This procedure may be used to investigate when the Gaussian wave packet method is appropriate for the simulation of a given process. [ABSTRACT FROM AUTHOR]