A study of the diabatic electronic representation within the Born-Oppenheimer approximation

This work considers the adiabatic-diabatic transformation for electronic states and the diabatic representation which follows accordingly. Two cases where ambiguity is encountered are discussed: one is the case where the reduced electronic manifold is not well separated everywhere in configuration space and the other is the case of conical intersections exemplified by the E ⊗ ε Jahn-Teller situation. It is shown that in both cases well defined diabatic states can be formed in most regions of configuration space.