Photodissociation Dynamics of Small Molecules: Collisionless and Collisional Processes

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In this project in the Experimental Physical Chemistry Program of the Chemistry Division, Reisler will examine fundamental state-to-state processes in unimolecular and bimolecular interactions, particularly systems undergoing unimolecular decomposition. The ultimate goal is to understand how to manipulate and direct chemical reactivity. The decomposition of the prototype molecule HNCO will be examined using sequential excitation and imaging techniques. When dissociation is too rapid to compete effectively with internal vibrational energy redistribution (IVR), signatures in NCO, NH, and CO product state distributions (PSDs) will reveal the presence of dynamical biases. Experiments are also proposed which are aimed at inducing selectivity and examining control of reactivity by several kinds of potential energy surfaces (PESs). Collisional studies will be extended to systems that involve two pathways, especially where spin-forbidden pathways are induced by collisions. Several sophisticated experimental techniques will be used, such as multiple resonance excitation and crossed pulsed molecular beams. Theoretical work will continue with Prof. Reinhard Schinke from Goettingen. In this project Prof. Reisler will study the influence of the stretching and bending motions of a molecule on the final outcome of the light-initiated dissociation of the molecule into fragments. The issues explored in this study include the identity of products formed and the final distribution of the various forms of internal energy into the fragment particles. Such fundamental examinations of the dynamics of chemical bond breaking have applications in many areas, such as an understanding of atmospheric chemistry and combustion processes.