TIME-RESOLVED EPR INVESTIGATION OF TRIPLET-STATE C-60 - TRIPLET-TRIPLET ANNIHILATION, CIDEP, AND QUENCHING BY NITROXIDE RADICALS

The paramagnetic species formed by laser flash irradiation of C60 in t oluene at room temperature was investigated by time-resolved EPR spect roscopy and assigned to the triplet state C-3(60). It is formed by int ersystem crossing with z magnetization M(z) almost-equal-to 0 and rela xes with T1 almost-equal-to T2 = 0.33 mus. Rate constants for triplet- triplet annihilation, k(TT) = 1.4 x 10(9) M-1 s-1 and triplet quenchin g by the TEMPO radical, k(q) = 2.4 x 10(9) M-1 s-1, were found, in sat isfactory agreement with previous flash photolysis work. CIDEP, genera ted by the radical-triplet pair mechanism, was analyzed and found to b e of equal size but opposite sign for the C-3(60) and TEMPO radical sp in systems.