Excitation of collective plasmon states in fullerenes

We present theoretical and experimental electron-energy-loss spectroscopy (EELS) results concerning the excitation of collective plasmon states in isolated fullerenes (gas targets). The large number of active electrons in a carbon cluster and the strong Coulomb interaction among them lead to a rich spectrum of collective states. States with total angular momentum up to L=8{} have a strong collective character. The equivalents of both {π} and {σ} plasmons in graphite are predicted for a whole range of carbon clusters C₂₀, C₆₀{C}₇₀$, and ${C}₁₀₀$. The theoretical results compare very well with experimental photoexcitation results in ${C}₆₀$ and ${C}₇₀$ and EELS data on gas targets ${C}₆₀$ and ${C}₇₀$.