Multiphonon excitation and quantum decoherence in neon scattering from solid surfaces

We present angle- and energy-resolved analysis of Ne scattering from a Ni(111) surface at moderate beam energy and surface temperature. Variation of the surface temperature allows the transition from a pure quantum regime, where single-phonon events are observed, to the classical regime, where multiphonon excitations are observed. The latter can be reproduced by classical calculations. Therefore, our data lie on the border between the coherent quantum regime and the incoherent classical regime.