TIME-RESOLVED EPR AND FOURIER-TRANSFORM EPR STUDY OF TRIPLET C-60 - DETERMINATIONS OF T1 AND THE C-13 HYPERFINE COUPLING-CONSTANT

Continuous wave (CW) and time-resolved (TR) EPR spectra of triplet C60 with partial and full C-13 enrichment in methylcyclohexane solutions after UV irradiation were obtained. Line broadening from C-13 satellites was observed. The C-13 hyperfine coupling constant was determined to be 0.06 G. Fourier transform EPR (FT-EPR) experiments with a resolution of 20 ns were carried out, and T1 was found to be 0.8 +/- 0.1 mus by fitting the intensity of the free induction decay signal to the modified Bloch equations. The relaxation time from FT-EPR is in excellent agreement with estimations from the line width of CW-EPR. Because the C-13 hyperfine coupling constant is so small, no distinct satellite lines were observed with C-13 in natural abundance at 200 K.