  In this paper we present calculations of single-particle excitation spectra
of neutral and three-electron-doped Hubbard C$_{60}$ molecules and monolayers
from large-scale quantum Monte Carlo simulations and cluster perturbation
theory. By a comparison to experimental photoemission, inverse photoemission,
and angle-resolved photoemission data, we estimate the intermolecular hopping
integrals and the C$_{60}$ molecular orientation angle, finding agreement with
recent X-ray photoelectron diffraction (XPD) experiments. Our results
demonstrate that a simple effective Hubbard model, with intermediate coupling,
$U=4t$, provides a reasonable basis for modeling the properties of C$_{60}$
compounds.
