Energy transfer cross sections in relation to generalized oscillator strengths for the donor–acceptor pair benzene–acetone

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Abstract
Generalized oscillator strengths have been determined for the ? 1B2u←? 1A1g transition in benzene and the ? 1A2←? 1A1 transition in acetone. From the data, and the spectroscopic data and analysis of other investigators, the generalized oscillator strengths for the reverse transition in benzene have been calculated approximately. Huo’s theory of energy transfer cross sections [J. Chem. Phys. 66, 3572 (1977)] and the generalized oscillator strengths have been used to calculate the cross section for the resonant energy transfer process benzene (? 1B2u) + acetone (? 1A1) → benzene (? 1A1g)+acetone (? 1A2). The energy transfer cross section calculated in this way is found to be 39 Å2 with an estimated uncertainty of ±5 Å2. The experimental value is 33±2 Å2 [K. Janda and F. S. Wettack, J. Am. Chem. Soc. 94, 305 (1972)]. Huo’s theory is based on the Born approximation, neglecting electron exchange. The agreement between calculated and observed cross sections shows that the Born approximation (without exchange) is holding even though the molecules are colliding with relative velocities in the thermal range.