Nonradiative transitions in benzene

A symmetric Rosen-Morse potential was assumed for the potential of the out-of-plane vibrations of benzene. Matrix elements and the respectiveS ₁ ?S ₀ nonradiative rates were calculated for several values of the anharmonicity constants and compared with the results obtained with a harmonic potential. Anharmonicities of the out-of-plane modes in benzene are found to decrease the values of the matrix elements and rates, thus leaving unresolved, a discrepancy between experimental and theoreticalS ₁ ?S ₀ rates for benzene. However, in molecules with distorted acceptor modes whose frequencies are higher in the optically excited, as compared to the acceptor state, increases of several orders of magnitude of the nonradiative rate could occur on introduction of Rosen-Morse type anharmonicities.