EXCITED-STATE PHENOMENA IN SOLID-STATE FULLERENE

Photoluminescence, photoconductivity and resonant Raman measurements a re performed to investigate the influence of high intensity illuminati on on the properties of Fullerenes. A highly nonlinear dependence of t he luminescence emission efficiency and lifetime is observed on increa sing the intensity. This nonlinear increase is associated with a drama tic shift to the red of the emission maximum. The photoconductive resp onse of the fullerenes is also seen to increase nonlinearly with input intensity. Temperature dependent measurements indicate that the nonli near processes are associated with an insulator-metal phase transition in the material. The transition is reversible and the observed photop hysical changes coincide with a reversible shifting of the characteris tic fullerene Raman lines to lower energies.