QUANTUM SCATTERING OF HEAVY-PARTICLES FROM A 10 K CU(111) SURFACE

Using low-energy nozzle beams of Ne, Ar, Kr, and N-2 gases, we have me asured the scattered elastic and inelastic intensities from a 10 K Cu( 111) surface, kept clean by pulsed laser heating. Our observations for heavy atoms such as Ar and Kr are consistent with a picture where the probability for elastic scattering at low surface temperature is inde pendent of particle mass m, as predicted by Burke and Kohn, and depend on m(1/2) at elevated temperatures. Rotational excitations reduce the elastic scattering of N-2 by more than an order of magnitude and weak en the phonon inelastic scattering.