Vibronic interaction in the lower electronic states of benzene

Abstract

In the present paper the pseudo Jahn-Teller interaction between the four lower electronic states of benzene is considered, with special reference to the mixing of the aBlu and 3Elu states through the e2g carbon-carbon stretching mode. First a review is given of the pioneering work of Liehr on the static problem, where the 'electronic Hamiltonian' is solved as a function of fixed nuclear coordinates. Results of a specific calculation are presented.Subsequently, the equations for the vibronic problem are set up by generalizing the methods proposed by Moffitt et al. and Longuet-Higgins et al. for the dynamic Jahn-Teller effect. These equations are then solved in the first (' pseudo-cylindrical ') approximation in which only the strong coupling linear in the displacements between the Blu and Elu states is considered. The results are discussed with reference to known properties of the phosphorescent state of benzene.

Photoionization-induced dynamics of the ammonia cation studied by wave packet calculations using curvilinear coordinates

“…This study was based on a vibronic coupling model [12][13][14] that included only linear coupling terms. It included the coupling of the non-degenerate ground state with the degenerate first excited state known as the pseudo-Jahn-Teller (PJT) effect [12,[15][16][17]. Indeed, a conical intersection [18,19] between ground and excited state was found in this study and fast but incomplete decay to the ground state was predicted.…”

Vibronic interaction in the lower electronic states of benzene

“…From our E.S.R. work on phosphorescent mesitylene in a trimethylborazole host [23] it was concluded that these two levels have quite different zero-field splittings (see also the next section), and it was speculated [1] that they might also differ substantially in their radiative lifetimes. A subsequent investigation of the phosphorescence of this system by Erlitz and Nieman [24], however, revealed that the lifetime increased by less than 5 per cent on cooling from 100 to 50K.…”

“…The first one, FpV(d~), expresses the direct Jahn-Teller interaction within the Elu pair, which here is a two-electron effect and therefore weak [5,1]. The last term, Gp2W(~), represents the quadratic correction related to the linear term KpU(d~).…”

“…This follows from the behaviour of the functions (1.5) under the operation R by which the molecule is rotated by 2rr/6 about its hexagonal axis. Namely, if oJ = exp (27ri/6), then [1] R All three coupling terms mix states differing in A and 1. In part I we only considered the leading one KpU(d~), which brings about interaction of the Blu electronic state with each member of the Elu pair.…”

“…In part I [1] we considered the vibronic interaction of the lower Blu and Elu states of benzene through the carbon-carbon stretching symmetry mode Q8. Our procedure was a generalization of the method by which Moflitt and Liehr [2] and Longuet-Higgins, 0pik, Pryce and Sack [3] treated the dynamic Jahn-Teller effect; its essence will first be summarized.…”