The photoluminescence and PL-detected magnetic resonance of C60 and C70

The X-band photoluminescence detected magnetic resonance (PLDMR) of C60 and C70 films and molecules isolated in toluene/polystyrene glasses is described. Both fullerene glasses have a PLDMR due to a triplet exciton delocalized over the entire molecule. However, the PLDMR of 3C70 strikingly differs from that of 3C60 in both linesbape and dynamics. These differences are due to the much longer lifetime of 3C70 which is consequently phosphorescent. The PLDMR of films indicates that the delocalized triplet is distorted by intermolecular interactions and reveals a half-field resonance consistent with thplet-triplet fusion. In addition, a broad ∼600G wide triplet powder pattern at g ≈ 2, its half-field resonance at g ≈ 4, and a narrow PL-enhancing resonance at g = 2. 0017 and 2. 0029 for C60 and C70 resp., are observed. This second triplet is believed to be localized on a pentagon or hexagon face adjacent to a neighboring molecule. A narrow (∼3. 3 G wide) PL-enhancing resonance is attributed to recombination oflong-lived charged polarons. The PLDMR ofphotooxidized and photopolymerized films of C60 and C70 is also described. Both processes quench the localized triplet, but PLDMR spectrum of photopolymerized 60 films reveal the presence ofa third triplet exciton delocalized across several molecules. © 1994 SPIE. All rights reserved.