JAHN-TELLER EFFECTS IN SUBSTITUTED BENZENE CATIONS .2. GAS-PHASE EMISSION-SPECTRUM OF 1,3,5-C6F3D3+ AND COMPARISON WITH 1,3,5-C6F3H3+

The emission spectrum of 1, 3, 5-C6F3D+3 in the 4376-5435 Å region has been photographed and vibronically analyzed. The transition is B̃2 A″2-X̃2E″. Vibrational frequencies were assigned using the isodynamic molecule method as previously done in analyzing the 1, 3, 5-C6F3H+3 spectrum. Out-of-plane a″2 and e″ modes are active in even quanta only and are associated with sequence bands a′1 and e′ modes are active in both odd and even quanta. The e′ mode activity is shown to be due to dynamic Jahn-Teller effects in the X̃2E″ state. A brief review of the relevant theory leads to a discussion of criteria for identifying Jahn-Teller spectral effects. Two importants parameters enter into the linear coupling model calculations: D, the interaction constant, and ω, the deperturbed frequency of the Jahn-Teller active mode. These parameters are determined by fitting calculated band positions and intensities to experimental results. It is shown how to resolve possible ambiguities in these determinations, D and ω values were obtained for four e′ modes of 1, 3, 5-C6F3D+3 and 1, 3, 5-C6F3 +3, modes 6, 7, 8 and 9. The corresponding Jahn-Teller barrier heights for interconversion between the lowest energy asymmetric configurations were evaluated for the two ions. © 1979.