Non-radiative transitions: competing interaction models

In the theory of non-radiative transitions, as in all internal transition theories, many different choices for the transition Hamiltonian are possible. The main emphasis of the paper is to show that different choices may yield transition rates which differ by orders of magnitude. Unitary transformations prove a natural means to mediate different interaction forms. Six different approximations are compared ('static', 'Condon', and four 'non-Condon' approaches). It is suggested that the lowest rate has to be taken, if more than a single result is valid for any given coupling strength.