THE SYMMETRY GROUPS OF NONRIGID MOLECULES - A LIE ALGEBRAIC AND GROUPCONTRACTION APPROACH

The description of the symmetry of non-rigid molecules is explored thr ough a Lie algebraic approach. It is shown that the abstract process o f contraction to an appropriate Lie algebra corresponds to restriction of molecular motion to regions located around the minima of a global potential. The contracted algebra may be determined by recasting the H amiltonian in terms of variables which vanish at global potential mini ma, and the resultant direct or semi-direct product group structure ac cords with that proposed by other workers. This approach is applied to two familiar problems of molecular symmetry, namely inversion through a potential barrier and hindered rotation; the results derived confir m and extend those obtained by other methods.