PULSED-EPR ON THE PHOTOEXCITED TRIPLET-STATE OF C-60

The photoexcited triplet state of C-60 has been investigated by the pu lsed EPR technique. A line shape analysis has been performed in order to determine the triplet spin dynamics in frozen and in liquid solutio ns. In frozen solution the EPR line shape reveals exchange narrowing w hich can be simulated rather well by assuming an exchange between the equivalent states of D-5d symmetry of the lowest triplet state. The de termined exchange rate turned out to be only weakly temperature depend ent and suggests that the dynamics is due to tunneling between Jahn-Te ller distorted states rather than to real molecular jumps. Measurement s on a modified C-60 molecule, where the high symmetry is reduced due to chemical substitution, support the above interpretation. In liquid solution the EPR signal of C-3(60) could be identified by means of ele ctron transfer reactions. The corresponding spin dynamics is analyzed.