Calculated Radiationless Transition Rates for Benzene and Deuterobenzene

Radiationless rates have been calculated for the B1u3⇝A1g1 transitions of benzene and perdeutero-benzene as well as for the B2u1⇝A1g1 transition of benzene. The rates were calculated using a model that considers the radiationless transition as a tunneling process between two multidimensional potential surfaces and assuming both harmonic and anharmonic vibrational potentials. The importance of anharmonicity for the radiationless transition rate provides a possible explanation of environmental effects on these rates. Whenever possible, experimental parameters were used in the calculation. To this end we have obtained experimental values for the anharmonicities of the carbon–carbon and carbon–hydrogen vibrations and the size of the lowest triplet state of benzene.