OPTICALLY DETECTED MAGNETIC-RESONANCE (ODMR) STUDY OF ISOLATED C-70 MOLECULES AND C-70 FILMS

The X-band ODMR of C-70 molecules isolated in a toluene/polystyrene (C-70:T/PS) glass and C-70 films is compared to that of C-60. As C-60:T/PS, the C-70 glasses exhibit only a triplet pattern at g approximate to 2, clearly due to an exciton delocalized over the molecule; however, it is strikingly asymmetric and narrower, due to the larger size of C-70 The ODMR of both C-60 and C-70 films includes a narrow photoluminescence-enhancing polaron resonance and full- and half- field narrow and broad triplet exciton patterns. As in the glasses, the narrow pattern is due to the exciton delocalized over the molecule and is narrower in C-70. The broad pattern is tentatively assigned to a triplet localized on a face adjacent to a neighboring molecule. In contrast to C-60 the ODMR of C-70 films is detectable up to 295 K, apparently due to the slower rotation.