Analytic description of highly excited vibration-rotational states of diatomic molecules: I. Construction of the description

The approach developed earlier for calculating the vibration-rotational spectrum of a diatomic molecule was substantially generalized. The method was based on constructing a perturbation series whose zeroth-order term describes the interaction of nuclei by using the Kratzer potential U(r)=A/r{sup 2}-B/r, the perturbation being represented as V(r)= {summation} {sub n}D{sub n}/r{sup n}. The generalization is concerned with constructing a perturbation series using a screened Kratzer potential, which provides the possibility of taking into account the realistic behavior of the internuclear potential for r{yields}{infinity} even in the zeroth-order approximation for a wide class of diatomic molecules and allows this series to be applied to describe the discrete vibration-rotational spectrum to be justified up to the dissociation limit. 11 refs.