Topological effects due to conical intersections: A model study of two interacting conical intersections

A model is presented to study the (weak) interaction between two conical in tersections (e.g., a dimer of two loosely bound molecules each characterize d by a conical intersection). The model is an extension of a previous model for a single conical intersection formed by an electron housed by a vibrat ing molecule [Baer and Englman, Mol. Phys. 75, 293 (1992)]. The main result of this study is that the intermolecular coupling removes part of the dege neracy of the global system and in turn forms a new degeneracy, but will no t affect the multivaluedness of the nuclear wave functions. (C) 1999 Americ an Institute of Physics. [S0021-9606(99)01344-6].