Observation and identification of the molecular triplet in C₆₀ thin films

The excited state properties of C₆₀ thin films have been probed at 77 K using Raman spectroscopy. The change in the Raman, A_2g mode of C₆₀, whose position is largely independent of temperature was monitored as a function of the excitation intensity at 514.5 nm. This mode, normally positioned at 1469cm^-1, was seen to shift to a lower Raman frequency with increasing laser intensity. Two excited state species have been identified. The first, at 1466cm^-1, has been associated with the molecular triplet of C₆₀, while the second species, at 1463cm^-1, has been speculated to be an excited state co-operative in the solid.