Frame transformation theory for heavy particle scattering: Application to the rotational predissociation of Ar–H₂

The frame transformation concept, which is standardly used in discussions of atomic and molecular Rydberg spectra, is applied to heavy particle scattering theory. It is shown how this approach permits the use of an optimal reference frame in the various different ranges of the scattering coordinate. It is further argued that the accuracy of the coupled states or p‐helicity decoupling approximations may be significantly improved without substantial additional computational effort especially for low energy scattering processes, through the use of frame transformation procedures. The method is then applied to the calculation of the photodissociation line shapes for the rotational predissociation of Ar–H₂ within the framework of generalized multichannel quantum defect theory (MQDT). It is shown how the use of the frame transformation procedure yields reasonably correct product rotational state distributions in situations where the standard coupled states or body‐fixed decoupling procedure fails even at the qualitative level. The paper also reviews the application of generalized MQDT to heavy particle scattering processes.