Symmetry Analysis of Molecules Consisting of Two Coaxial Rotors Using the Extended Permutation-Inversion Groups

A general method for constructing permutation-inversion groups and their extensions to molecules containing two coaxial rotors is presented. Symmetry species of the dipole moment, tensor of polarizability, and total angular momentum operator are determined. General infrared and Raman selection rules, symmetry classifications of rotorsional, rotational, and torsional wavefunctions are derived. Theory is illustrated for the H3D+2 complex.