Applications of the generator coordinate approximation to diatomic systems. II. Dunham analysis of vibration–rotation spectra

It is shown how a Dunham series can be derived within the generator coordinate approximation. General kernel expansions are combined with order by order angular momentum projection and generator coordinate perturbation theory. The comparison of Born–Oppenheimer and generator coordinate kernal coefficients yields a clear identification of nonadiabatic effects incorporated in the generator coordinate approximation.