Nonadiabatic molecular dynamics simulation of ultrafast pump-probe experiments on I2 in solid rare gases

Recent experimental studies of both A and B state photoexcitation of I2 and the ensuing many-body dynamics in rare gas matrices by Apkarian and co-workers are simulated using the methods we presented in an earlier work combining nonadiabatic molecular dynamics with semiempirical diatomics-in-molecules ~DIM! excited state electronic structure techniques. We extend our DIM methods to compute the ion pair states of the I2-rare gas crystal system and use these states together with a model of the configurational dependence of the electronic dipole operator matrix elements to calculate the time resolved probe absorption signals in these pump probe experiments using a simple golden rule result. Our computed signals are in remarkable agreement with experiments and we use our calculations to provide a detailed microscopic analysis of the channels to predissociation and recombination underlying these experiments. © 1997 American Institute of Physics. @S0021-9606~97!02017-5#