SPIN DYNAMICS OF PHOTOEXCITATIONS IN C-60 AND C-70

We have used absorption detected magnetic resonance (ADMR) spectroscopy to study the spin dynamics of spin 1/2 and spin 1 photoexcitations in C-60 and C-70, in Molecular and solid-state forms. In C-60 molecules dispersed in polystyrene matrix (C-60:PS), two S = 1 powder patterns were observed at 4 K; they collapse towards the central g approximate to 2 magnetic resonance line with increasing temperature. We fit the results with a model that relates the two observed triplets with two Jahn-Teller distortion levels, respectively, subject to a temperature dependent pseudo rotation dynamics. In C-70:PS, we found that a S = 1/2 signal, which is associated with existing radicals in the sample, accompany the S = 1 ADMR signal. In sublimed C-60 and C-70 films, in addition to the triplet excitations with a quenching ADMR signal, we found an enhancing spin 1/2 ADMR signal. We explain this feature as due to charge separation, which uniquely occurs in sublimed films with excitation above the respective C-60 and C-70 energy gap.