Knowledge Bank

The molecular symmetry group (PE-group) is used for the classification of eigenfunctions and evaluation of selection rules for molecules having one, two and three $CH3$ tops and $Cs$, $C2u$, and $C3v$ symmetry, respectively. The rotation-internal-rotation and torsional-vibration problem is considered. It is shown that symmetry groups generated by associated elements of the PE-group are essentially the same symmetry groups used earlier for treating the same problems.