On the singlet excited states of C70 and C60

Abstract

The fullerenes C70 and C60 have been studied by excitation and luminescence spectroscopy. Highly resolved phosphorescence-excitation spectra of C70 in n-pentane at 1.5 K are reported. Besides the origin and e1′ vibronic bands of the lowest-energy A2′←S0 excitation, the origin, and an a1′ vibronic band of the E1′←S0 excitation are assigned. For both C70 and C60 the fluorescence spectrum changes with temperature, which is explained in terms of thermally induced population of excited states above S1. For C70, this concerns the E1′ state and the corresponding fluorescent state is found to be 130 cm−1 above the A2′ state in decalin/cyclohexane. For C60 in the same matrix, it concerns the state of predominant Gg character at 85 cm−1 above the T1g state.