Intramolecular dynamics of collisionally excited metal⋅⋅⋅ligand complexes in the energy localization range

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Abstract
We report trajectory calculations on intramolecular energy flow and bond dissociation of a model system OC⋅⋅⋅Pt⋅⋅⋅CO in a collision energy range, where the energy transfer to the complex localizes in one of the two Pt⋅⋅⋅CO bonds. The collision model is an Ar atom incident on the left-hand-side terminal atom of the complex containing a vibrationally excited ligand (OC*⋅⋅⋅Pt⋅⋅⋅CO or OC⋅⋅⋅Pt⋅⋅⋅CO*) in a collinear configuration. In this energy range, essentially all of the energy transferred to the complex localizes in the right-hand-side Pt⋅⋅⋅CO bond for a time corresponding to many vibrational periods before dissociation or intramolecular energy flow occurs. The existence of this energy localization time zone and its effect on intramolecular dynamics are discussed in detail at various collision energies. Energy localization leads to long delay for bond dissociation and strong dependence of bond dissociation on the initial excitation site. Time delay for the dissociation of the left-hand-side Pt⋅⋅⋅CO bond is particularly long, and this inefficient dissociation process is discussed in terms of intramolecular recrossing of the vibrational energy across the heavy mass barrier. At the threshold, dissociation always occurs at the side where the excited ligand is present: Ar+OC*⋅⋅⋅Pt⋅⋅⋅CO→Ar+OC*+Pt⋅⋅⋅CO or Ar+OC⋅⋅⋅Pt⋅⋅⋅CO* →Ar+OC⋅⋅⋅Pt+CO*.