Hindered asymmetric top states for chemical reactions

Abstract

A computational method for development of hindered asymmetric top rotational wavefunctions for atom–diatom chemical reactions is presented. The external rotation of the triatomic system is that of a nonrigid asymmetric top that is in no way hindered. Internal rotation (bending) of the system is described by hindered rotor functions of the internal angle. The internal rotation‐bending angle is the natural collision coordinage γ; a rotating‐axes system located by Euler angles is used to orient the three particle triangle. The basis states are obtained as linear combinations of hindered symmetric top states by perturbatively adding on Coriolis and asymmetry terms in the Hamiltonian while allowing limited configuration interaction among unperturbed levels. The coupling mixes states of different K (projection of the total angular momentum on the rotating Z axis). A single rotational potential minimum is considered in computing symmetric and asymmetric top energy level correlation diagrams. The usefulness of this rotational basis in close‐coupling reactive scattering calculations is discussed.