Knowledge Bank

It is shown that the vibronic coupling problem in molecules with two nearly degenerate electronic states and in dimers have the same mathematical form---a$2\times 2$ matrix Hamiltonian. This equation is reduced to a one dimensional form and solutions are obtained in two limiting cases. The one corresponds to vibrational borrowing, the other to a pseudo Jahn-Teller effect. The one dimensional equations contain a non-local potential.