Vibronic interaction in the lower electronic states of benzene

Abstract

Results are given of some calculations on the (pseudo Jahn-Teller) vibronic interaction between the lower excited Blu and Elu triplet states of benzene in which two active vibrations in the pseudo-cylindrical approximation are considered. A satisfactory account is given of the relative intensities of the six characteristic bands in the phosphorescence spectrum which involve one or three quanta of the active modes, and also of the energy of the prominent doublet in the absorption spectrum first observed by Burland et al. In addition interaction with a crystal field is considered: a simple potential affords a quantitative explanation of the splitting of the doublet in the absorption spectrum and also of the crystal field induced intensities of the 0-0 bands in absorption and emission.

Modern Aspects of the Jahn−Teller Effect Theory and Applications To Molecular Problems

“…The same PJT coupling in C 6 H 6 + and C 6 D 6 + between the two states, B̃ and C̃, was employed 341 to interpret the vibrationally resolved photoinduced Rydberg ionization spectra of the dipole-forbidden C̃ 2 E 2g ← X̃ 2 E 2g transition. For the calculations, the authors 341 employed a two-mode PJT model. , The JT coupling parameters used to fit the calculated spectral lines to the observed ones are given in Table .…”

“…For the calculations, the authors 341 employed a two-mode PJT model. 350,351 The JT coupling parameters used to fit the calculated spectral lines to the observed ones are given in Table 16.…”

The observation of strong pseudo-Jahn–Teller activity in the benzene cation B̃ 2E2g state

“…A very similar form of pseudo-JT dynamic coupling was presented in an excellent series of papers by van der Waals and co-workers. [50][51][52] They developed a model which described the coupling between the 3 B 1u and 3 E 1u electronic states of neutral benzene via two e 2g vibrational modes. Their coupling case is, in essence, very similar to the one we are considering, the major differences being the relative ordering and the angular momenta of the electronic states.…”

Mass-Analyzed Threshold Ionization Spectra of C6H6+ and C6D6+ Obtained via the 3B1u Triplet State

“…The appearance of the 8 0 1 hot band in the gas phase MATI spectrum is of interest since the ν 8 frequency in the triplet state (229 cm -1 ) is significantly lower than in S 0 and S 1 (∼1500 and ∼1600 cm -1 , respectively) and has been the subject of many papers over the past 40 years. ,,,,− The interest in ν 8 in the 3 B 1u state lies in the fact that the 3 B 1u state is pseudo-JT active, and must vibronically couple to the 3 E 1u state to gain any oscillator strength in phosphorescence. This coupling can only occur through the four e 2g modes, and it has been shown that the ν 8 stretching mode is the most likely vibration to induce this coupling. , The strong appearance of ν 8 in the triplet MATI hot band spectrum emphasizes the strong vibronic interaction of that mode in the cation ground state.…”