Experimental evidence for 400-meV valence-band dispersion in solid ${\mathrm{C}}_{60}$

Angle-resolved electron distribution curves have been measured for two different excitation energies on heteroepitaxial ${\mathrm{C}}_{60}$(111) films. At ħω=29 eV, the limited ${\mathit{k}}_{\mathrm{\parallel }}$ resolution together with broadening induced by vibronic excitations results in a weak dependence of the peak positions and line shapes of the photoemission features on the emission angle. We demonstrate that at the low photon energy of ħω=8.1 eV the ${\mathit{k}}_{\mathrm{\parallel }}$ resolution becomes sufficient to resolve two bands in the feature derived from the highest-occupied molecular orbital which show a dispersion of the order of 400 meV.