Luminescence from C60 single crystals in glassy phase under site-selective excitation

Luminescence from C60 single crystals has been investigated at liquid He temperature under selective excitation into the tail part below the fundamental absorption edge. Luminescence line narrowing is observed for resonant excitation, in which a characteristic vibrational quantum is found ∼420 cm−1 in the excited state. It is revealed that the spectrum which has been known as photo-luminescence from C60 single crystals is an superposition of site-selective luminescence from several localized states. Such inhomogeneity is most likely to arise from fluctuation of the intermolecular orientational correlation in a pair of C60 molecules over which the excitation is delocalized.