Comparative ESR study of C60 and C70 radical anions produced in γ-irradiated organic solid solutions at 77 K

ESR spectra of C70 radical anions were detected for C70/methylcyclohexane (MCHX) and C70/2-methyltetrahydrofuran (MTHF) solid solutions which were γ-irradiated at 77 K and subsequently annealed at 107–117 K. The ESR spectrum for C70/MCHX was a singlet which was ascribed to C70−, and was flanked by a pair of satellites due to matrix proton spin flip lines. The ESR spectrum for C70/MTHF was a superposition of a singlet and a deformed doublet. The latter was unstable and disappeared at 109 K, and was tentatively ascribed to C702−. ESR spectra of C60 radical anions were partly reinvestigated and are compared to those of C70. The relative electron attachment efficiencies for C60 and C70 at 77 K were estimated, and the former was about twice as large as the latter. Isothermal decay at 77 K was observed for both C60 and C70 radical anions.