Abstract
In this work we present new results on electron transfer (ET) rates in the hexamethylbenzene/tetracyanoethylene charge-transfer (CT) complex in supercritical carbon dioxide. The electron transfer process from the excited state of this CT complex is considered to correspond to the highly exoergic "Marcus inverted region", and extensive studies have been performed on the role of the intramolecular vibrational modes and the solvent relaxation[1-4]. The recent theoretical study on the absorption, fluorescence, and Raman spectra of this CT complex in CCl4 with a common model based on Marcus' and Jortner's theory[4] requires a large (2450 cm-1) solvent reorganization energy λs, and overestimates the ET rate. The large reorganization energy has been ascribed to the inseparability of the low frequency intermolecular complex vibrations and the solvent relaxation. The study using a supercritical fluid as solvent is a suitable approach to answer the problem of the mode separation:i.e., in dilute gases, there should be little contribution of the solvent reorganization energy, and the effect of the solvent on the ET process can be extracted from its density dependence.
© 1996 Optical Society of America
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