Frenkel and charge-transfer excitons inC60

Abstract

We have studied the low-energy electronic excitations of ${\mathrm{C}}_{60}$ using momentum dependent electron energy-loss spectroscopy in transmission. The momentum dependent intensity of the gap excitation allows for a direct experimental determination of the energy of the ${}^{1}{H}_{g}$ excitation and thus also of the total width of the multiplet resulting from the gap transition. In addition, we could elucidate the nature of the following excitations---as either Frenkel or charge-transfer excitons.