We report an empirical potential energy surface (PES) for the Ar/Pt(111) system. We also report new atomic beam scattering data for this system, extending up to collision energies of >7 eV. The PES is based on a pairwise sum of noncentral potentials. Molecular dynamics calculations on this PES are found to be in generally good agreement with scattering data spanning the thermal and structure scattering regimes and with published measurements of the trapping probability as a function of incidence energy, E(i), and angle, theta(i). An important exception to the overall good agreement between experiment and calculation is that we are not able to account fully for the observed degree of energy transfer for E(i) cos(2) theta(i) > 3 eV. We suggest that the excess energy transfer is due to coupling to electron-hole pairs.