The Jahn-Teller and pseudo-Jahn-Teller effects in the low-lying electronic states of 1,3,5-trifluorobenzene radical cation

Static and dynamic aspects of the multimode Jahn-Teller (JT) and pseudo-Jahn-Teller (PJT) interactions in the low-lying electronic states of 1,3,5-trifluorobenzene radical cation (TFBZ(+)) are investigated by an ab initio quantum dynamical approach. The electronic ground state ((X) over tilde (2) E '') of TFBZ(+) is energetically well separated from its excited states. The first three excited electronic states ((A) over tilde (2) A(2)'', (B) over tilde (2) E' and (C) over tilde (2) A(2)') are however, energetically close. A sequence of low-energy conical intersections underlying the JT and PJT interactions among these electronic states is established. Nonadiabatic effects due to these intersections on the vibronic dynamics are examined in detail. The theoretical results are compared with the low resolution and also better resolved experimental data. The impact of increasing fluorination on the structure and dynamics of the excited states is discussed in relation to the parent benzene radical cation and its mono-and di-fluoro derivatives.