Excimer Model for Photoluminescence in Single-Crystal C₆₀

We report the photoluminescence spectrum of well characterized, epitaxially grown single-crystal C 60 thin films. The highly regular and reproducible spectral features observed can be explained by a simple molecular model which takes into account enhanced coupling of an excited C 60 molecule with its nearest neighbor. This model provides an identification of all the observed spectral features at low temperature including a qualitative understanding of the relative peak height ratios, as well as the observed temperature dependence of the photoluminescence spectrum.