Chaos and incoherence in a model of multiple-photon excitation of molecular vibrations.

We consider in detail our earlier classical model of multiple-photon excitation of molecular vibrations in an infrared laser field, wherein the observed fluence dependence of the process is associated with chaotic variations of a pumped mode. We focus our attention first on a quasicontinuum model of background vibrational modes, which provides us with a dynamical system in which the role of chaos is neatly interpretable. Then we consider a model with only a finite number of background modes in order to corroborate the conclusions drawn from the quasicontinuum model.