Electron spin polarization transfer and radical-triplet pair polarization in nitroxide-C60 derivative systems

Nitroxide free radical/[60]fullerene derivative liquid solutions photoexcited by visible laser pulses are investigated by time-resolved EPR. Both radical and triplet excited fullerene spin-polarized EPR signals are observed. Their time evolution is examined in terms of CIDEP effects due to electron spin polarization transfer from the initially polarized triplet to the nitroxide and to spin polarization generated by the radical triplet pair mechanism. Radical and triplet spin relaxation times and rate constants for the processes of polarization transfer and radical triplet pair mechanism are obtained.