Direct measurement of velocity distributions in argon beam--tungsten surface scattering

Velocity distributions for Ar atoms scattering from a clean, polycrystalline tungsten surface have been measured for a wide range of incident supersonic beam energies 300 K < (1/2) m/k<2000 K, and surface temperatures 350 K=0.83 +0.20 over the entire range of energies and temperatures for 450 angle of incidence and observation in the specular direction (KE/sub e/, KE/sub i/, and KE/sub T/s are the kinetic energy of the exiting Ar, the incident Ar, and the Ar in equilibrium at the surface temperature, respectively). The proportionality relationship is nearly the same for observation in the normal direction. The collision-caused spread in velocities is linearly proportional to the surface temperature, and substantially independent of incident energy. Tangential momentum accommodation is also discussed