PULSED EPR ON THE PHOTOEXCITED TRIPLET-STATE OF C(60)-FULLERENE

We report on the observation of two different triplet states in photoexcited C60 fullerene molecules. The following fine structure parameters were determined from spectral fits to the triplet powder spectrum: \D1\ = 0.0 1 17 cm-1 (12.5 mT), \E1\ = 0.0014 cm-1 (1.5 mT) and \D2\ = 0.0047 cm-1 (5 mT), \E2\ = 0.0 cm-1. Below 10 K mainly triplet 1 was observed, whereas triplet 2 appeared only with increasing temperature. It is thermally activated with an activation energy DELTAE almost-equal-to 17 meV. Due to motional narrowing the parameters D1 and E1 decrease slightly at higher temperatures. Depopulation kinetics as well as spin-lattice relaxation rates were determined.