Abstract
The double group of the molecular symmetry group of ferrocene is used to classify the rotational and torsional wavefunctions and the ‘approximate normal coordinates’ of the molecule. The approximate normal coordinates do not depend on either the torsional angle or the torsional quantum number, and from their symmetry species the infra-red and Raman selection rules are determined. It is also shown how an ultra-high resolution analysis of some of the infra-red bands might yield the height of the torsional barrier.