Semiclassical molecular dynamics simulations of intramolecular proton transfer in photoexcited 2-(2 '-hydroxyphenyl)-oxazole

A full-dimensional excited state potential energy surface is constructed, a nd the proton transfer dynamics associated with the keto-enolic tautomeriza tion reaction in photoexcited 2-(2'-hydroxyphenyl)-oxazole is simulated acc ording to an approximate version of the semiclassical initial value represe ntation method introduced by Miller and co-workers [V. Guallar, V. S. Batis ta, and W. H. Miller, J. Chem. Phys. 110, 9922 (1999)]. The full-dimensiona l potential energy surface is developed according to an nb initio reaction surface model obtained at the CIS Level of quantum chemistry. Proton transf er is found to be substantially affected by isotopic substitution, and sign ificantly coupled to the internal oxazole-hydroxyphenyl in-the-plane bendin g mode. The nascent tautomer is found to be stabilized primarily through vi brational energy redistribution into all of the remaining in-the-plane vibr ational modes. The accuracy of the methodology is verified by reducing the dimensionality of the system and comparing our semiclassical results with f ull quantum mechanical calculations. (C) 2000 American lnstitute of Physics . [S0021-9606(00)01845-6].