Collective plasmon excitations inC60clusters

Abstract

The electromagnetic response function of a ${\mathrm{C}}_{60}$ cluster is calculated using linear-response theory. We find that the valence electrons are quite delocalized and show collective excitations. In the low-energy part of the excitation spectrum, the lowest allowed transition at ħω≊3 eV is strongly screened, and the other transitions below 6 eV are moderately screened, in agreement with experiment. We also predict a giant collective resonance at an unusually high energy of ≊20 eV.