Probability of selective fragmentation of valence bonds of polyatomic organic molecules exposed to IR radiation

A model for calculating the fragmentation probability of a specific valence bond of an organic molecule exposed to IR radiation is proposed. The model is based on excitation by an external periodic electric field of many independent collective vibrational states (excimoles) in molecular substructures containing identical ordered diatomic valence bonds with a dipole moment. It is assumed that the eximole vibrational energy cannot be concentrated on one valence bond of a substructure. It is shown that radiationless transfer of excimole energy to a specific molecular valence bond that does not belong to the identical dipole substructure may result in molecular dissociation. An analytical expression for the molecular dissociation probability function is obtained in the framework of the model, which demonstrates significant dependence of this function on the spacing between the centers of mass of a breaking trap bond and the adjacent diatomic bond of the subsystem. For the case of fragmentation of lucine and isolucine isomers, this result has been experimentally verified.