Spin dynamics of triplet photoexcitations in C60: evidence for a dynamic Jahn-Teller effect

We have used the absorption-detected magnetic-resonance (ADMR) technique to study the spin dynamics of triplet photoexcitations in C60 molecules dispersed in polystyrene glasses. We found that the ADMR spectra contain two triplet powder patterns A and B with substantial spin reorientation dynamics, which increases with the temperature. The spin dynamics of triplet A are successfully modeled by a dynamic Jahn-Teller effect, where the spin reorientation process is among six degenerate D5d deformations of the excited C60 molecule. Triplet B, however, is extrinsic in origin, with substantially different spin dynamics.