Program

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Monday June 22

Mo1: Surface scattering and chemistry

Chair: U. Höfer, Marburg, Germany

Contributed talk

Hyperthermal atom scattering from surfaces

J. R. Manson¹ and W. W. Hayes²

¹Department of Physics and Astronomy, Clemson University, Clemson, SC 29634, USA

²Physical Sciences Department, Greenville Technical College, Greenville, SC 29606, USA

There have been a number of recent experiments reporting measurements of angular distributions of hyperthermal rare gas atoms scattering from metal and insulator surfaces. The experiments for scattering from metal surfaces usually show broad peaks whose most probable final angles are either sub-specular or supra-specular depending on initial conditions. The scattering from insulators can show rainbow features caused by the corrugations of the surface. The authors have developed a semiclassical theory for atomic scattering that includes the effects of surface corrugation [1, 2]. When extended to the classical limit of large projectile masses, high incident energies and large surface temperatures this theory is capable of explaining heavy rare gas scattering even in cases where rainbow features due to large surface corrugations are present. Examples will be shown for Ne, Ar and Xe scattering from Ru(0001), graphene covered Ru(0001), and LiF(001). The comparisons of theory with the available experiments suggest the following predictions for further experimental measurements. First, the comparisons of rare gas scattering from Ru(0001) and single-layer graphene covered Ru(0001) suggest that Os(0001) and graphene covered Os(0001) should be highly reflective to rare gas scattering. These results further suggest that Os and graphene covered Os should be highly reflective even under quantum mechanical conditions such as for scattering of He atoms with incident energies in the meV range. Second, the study of heavy rare gas scattering from metal surfaces predicts that the most probable final angle of the observed angular distributions will be sub-specular at low incident energies and will smoothly shift to larger final angles and eventually become supra-specular with increasing incident energy. This implies that, for a given system of projectile atom and metal surface, there will be an incident "recovery" energy at which the most probable final angle of the observed angular distribution will appear at the specular position.

[1] W. W. Hayes and J. R. Manson, Phys. Rev. Lett. 109, 063203 (2012)

[2] W. W. Hayes and J. R. Manson, Phys. Rev. B 89, 045406 (2014)