Jahn-Teller distortions in C₆H₃F₃ ⁺ and C₆H₃Cl₃⁺

The simple, linear theory of Jahn-Teller coupling is reviewed. The effects of quadratic terms and mode mixing are incorporated into the theory. It is then applied to the previously determined vibronic structure of the organic radical cations, C₆H₃F₃⁺ and C ₆H₃Cl₃⁺. Quadratic effects are shown to be small but not neglible for these ions, and mode mixing effects are quite significant. Jahn-Teller distortion parameters are determined for three modes including the benzene ring in-plane stretching and bending modes. These parameters are used to obtain the distorted geometry of the ions at the minima of their potential energy surfaces and the energy lowering due to the Jahn-Teller effect.