Qualitative Analysis of Torsional Motion in Molecules with a Center of Inversion: II. The Ethylene Molecule ~(12)C_2H_4

摘要

Using the concept of the chain of symmetry groups, a qualitative analysis of torsional motion in molecules whose equilibrium configurations possess a center of inversion is performed. The analysis includes the classification of stationary states and the construction of effective operators of physical quantities describing intermolecular motion in the presence of internal rotation. The set of independent energy-equivalent equilibrium configurations of a molecule that is required for the analysis is specified with the help of the coordinate spin operator. For molecules of the given type with a linear framework and two identical torsional tops, guidelines are given that may be used to separate rotational and torsional motions in the case where they cannot be described independently.