摘要
Jahn and Teller have shown that if the electronic state of a nonlinear molecule is orbitally degenerate, a distortion lowering the molecular symmetry tends to arise so that the degeneracy is removed. Recently, the dynamical aspect of the Jahn-Teller effect has been discussed in a number of papers. The so-called dynamical Jahn-Teller effect is essentially the dynamics of coupling between an ion in a degenerate electronic state and molecular vibrations (or phonon in a crystal). The articles cited in [2] deal almost always with the weak coupling, i.e., when the energy of static distortion of electrons is smaller than the energy of phonon. The energy levels of electron-vibration system are obtained by means of a perturbation theory, in which the expansion parameter is the
