EXCIMER MODEL FOR PHOTOLUMINESCENCE IN SINGLE-CRYSTAL C-60

We report the photoluminescence spectrum of well characterized, epitax ially grown single-crystal C-60 thin films. The highly regular and rep roducible spectral features observed can be explained by a simple mole cular model which takes into account enhanced coupling of an excited C -60 molecule with its nearest neighbor. This model provides an identif ication of all the observed spectral features at low temperature inclu ding a qualitative understanding of the relative peak height ratios, a s well as the observed temperature dependence of the photoluminescence spectrum.