A PHOTOLUMINESCENCE STUDY OF $C_{60}$ AND $C_{70}$

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1992

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Ohio State University

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Since their discovery, there has been considerable interest in the spectroscopic characterization of fullerenes, in particular the $C_{60}$ (Buckminsterfullerene) and $C_{70}$ forms that may be produced in reasonable yields using a method described by Kratschmer et al. Arbogast et al. determined a number of important photophyscial properties of $C_{60}$ in hexane and benzene solutions, but were unable to detect either fluorescence or phosphorescence from $C_{60}$ at room temperature. However, a triplet state was detected by triplet-triplet transient absorption measurements, and photoquenching studies placed the triplet state energy between 11,500 and $14,500 cm^{-1}$. We have obtained luminescence spectra of $C_{60}$ and $C_{70}$ in glassy toluene solution at 77K and as neat solids at 5K. The $C_{70}$ spectrum consists of two band systems each with resolved vibronic structure. The red system of $C_{70}$ begins at $15,012 cm^{-1}$, exhibits a lifetime of $<20$ $\mu$sec and is assigned as $S_{1}\rightarrow S_{0}$ fluorescence. The infrared emission system begins at $12,614 cm^{-1}$, decays with a 30 msec. lifetime and is assigned as $T_{1}\rightarrow S_{0}$ phosphorescence. Several Raman modes are observed as combination bands in the infrared system. However, all of the prominent features cannot be assigned to a single, orbitally allowed transition.""

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Author Institution: Department of Chemistry, The University of Michigan

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