Models for Vibrational Energy Disposal

Dynamic Models for Vibrational Energy DisposaL —Busch and Wilson identified 

The earliest interfragment model was developed by Holdy, Klotz, and Wilson and its predictions were compared with the then available data for the near u.v. photodissociation of ICN (though these have since been questioned, see section S). Like many of the models which followed it, both semi-classical and quantum mechanical, it incorporated the quasi-diatomic approximation. This assumed that the molecular vibrational motion could be separated into pure bond vibrations, and that in the dissociation of a triatomic molecule, e.g. 

With this type of description, photo-excitation is assumed to prepare the parent molecule at the turning-point of a classical oscillation, localized on the bond which is to break. Since the interatomic potential is now repulsive, the system b ins to execute a half-collision and its dynamics can be treated on the basis of classical collision theory. Briefly, this leads to the equation 

Po-v is the probability of an oscillator emerging in the levd v, assuming it to have been unexcited at the initiation of the recoil. 

In either case, a Frandc-Condon description can be adopted to estimate the final distributions over vibrational states in the photofragment. 

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