AN EFFECTIVE HAMILTONIAN FOR AN ELECTRONICALLY EXCITED SOLUTE IN A POLARIZABLE MOLECULAR-SOLVENT

An effective Hamiltonian suitable for non-adiabatic molecular dynamics simulations is derived for the low-lying electronic states of a molec ular ion interacting with an assembly of polarizable solvent molecules . The Hamiltonian includes both induction and low-frequency dispersion effects. It is based on a molecular treatment of the solvent, but is similar to effective Hamiltonians that treat the solvent as a dielectr ic continuum. The electronic structure of the solute is described in a space defined by the low-lying electronic states of the isolated mole cule, and no assumptions are made about the form of the basis states. The effective Hamiltonian uses distributed multipoles and distributed transition multipoles, both of which may be obtained from ab initio ca lculations, to describe the charge distribution and polarizability of the molecular ion.