The Jahn-Teller system E x b_1 + b_2 has a particular degeneracy, where the
vibronic potential has an elliptical minimum. In the general case where the
ellipse does not reduce to a circle, the classical motion in the potential is
chaotic, tending to trapping near one of the extrema of the ellipse. In the
quantum problem, the motion consists of correlated tunneling from one extremum
to the opposite, leading to an average angular momentum reminiscent of that of
the better known E x e dynamic Jahn-Teller system.Comment: 7 eps figures, revtex. To be published, Phys. Rev.