The implications of the Jahn-Teller theorem are discussed with special reference to the case where the forces tending to lower the symmetry of electronically degenerate molecular states are of the same order as the restoring forces encountered during typical vibrations. It is shown that the resulting dynamical situation may be described as a particular kind of coupling between low-frequency electronic motions and nuclear modes.

• Received 8 October 1956

DOI:https://doi.org/10.1103/PhysRev.106.1195