A complete quantum description of an ultrafast pump-probe charge transfer event in condensed phase

An ultrafast photoinduced charge transfer event in condensed phase is simulated. The interaction with the field is treated explicitly within a time-dependent framework. The description of the interaction of the system with its environment is based on the surrogate Hamiltonian method where the infinite number of degrees of freedom of the environment is approximated by a finite set of two-level modes for a limited time. This method is well suited to ultrafast events, since it is not limited by weak coupling between system and environment. Moreover, the influence of the external field on the system-bath coupling is included naturally. The surrogate Hamiltonian method is generalized to incorporate two electronic states including all possible system-bath interactions. The method is applied to a description of a pump-probe experiment where every step of the cycle is treated consistently. Dynamical variables are considered which go beyond rates of charge transfer such as the transient absorption spectrum. The parameters of the model are chosen to mimic the mixed valence system $({\mathrm{NH}}_3{)}_5\mathrm{RuNCRu}(\mathrm{CN}{)}_5^{-}.$