H-CIRCLE-TIMES-H - A JAHN-TELLER COUPLING THAT REALLY DOES REDUCE THEDEGENERACY OF THE GROUND-STATE

In all linear Jahn-Teller (JT) systems studied to date, the ground sta te, after allowing for the vibronic interaction, has always been of th e same symmetry as the original electronic state. Furthermore, the gro und state remains the same symmetry for all coupling strengths. We now report results for the H x h JT system (as occurs in various states o f the C-60 molecule) when this is not the case. There are two possible types of JT effects in this system, depending upon whether D-3d or D- 5d extrema are absolute minima. For the case of D-3d minima, we find t hat for couplings above a certain value the ground state is an A-type singlet, rather than the expected H-type quintet.