Rotating hinge dynamics of CO₂HF: classical mechanics and semiclassical quantization

Abstract

Classical and semiclassical aspects of vibrational-rotational coupling in the CO₂HF complex are investigated by use of a rotating hinge model, in which the vibrationally averaged HF and CO₂ arms of the hinge are treated as rigid. Coexisting librational and precessional modes of bending-rotational motion are observed. Given that the bending potential has a dominant quartic component, Einstein-Brillouin-Kramers (EBK) semiclassical quantization yields remarkably accurate rotationless energy levels, but primitive quantization is found to omit certain states and to overlook classically forbidden l-type doubling effects. These deficiencies are remedied by a uniform quantization procedure, based on a timescale separation argument that allows reduction to a one-dimensional pendulum-like model.