Photoluminescence of molecular C70 at 1.5 K. On the nature of the lowest excited states

We report Shpolʹskii-type luminescence spectra of C70 in n-pentane at 1.5 K with vibronic linewidths of 3 cm−1. The vibronic structure of both fluorescence and phosphorescence has been unravelled. The fluorescence intensity largely shows up in vibronic bands corresponding to transitions to ground-state infrared-active vibrational modes and it is concluded that the first excited singlet state of C70 in alkanes is of A′2 character.