Scattering of Argon Beams with Incident Energies up to 20 eV from a (111) Silver Surface

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Abstract
Angular scattering distributions for argon atoms incident on well-characterized epitaxially deposited (111) Ag surfaces have been measured for incident-beam energies up to approximately 20 eV. The scattering pattern is a specularly directed single lobe. Its width increases as the incident-beam energy increases, as is expected for structural scattering. The direction of the maximum scattered signal is about 3° supraspecular for the entire energy range (3–18 eV) covered in these experiments. The expected increase of the scattered-beam peak amplitude with increase of beam energy is observed at the lower energies. A peak-amplitude decrease with beam-energy increase at higher beam energies is observed here for the first time. Bombardment of the surface with an argon beam with energy above an observed threshold energy reduced significantly the scattering-distribution width for a thermal-energy helium-beam probe. It is found that, at least under certain surface conditions, a high-energy argon beam is a more sensitive surface probe than is a thermal-energy helium beam.