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Quantum reflection of helium atom beams from a microstructured grating

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 نشر من قبل Bum Suk Zhao
 تاريخ النشر 2008
  مجال البحث فيزياء
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We observe high-resolution diffraction patterns of a thermal-energy helium-atom beam reflected from a microstructured surface grating at grazing incidence. The grating consists of 10-$mu$m-wide Cr strips patterned on a quartz substrate and has a periodicity of 20 $mu$m. Fully-resolved diffraction peaks up to the $7^{rm th}$ order are observed at grazing angles up to 20 mrad. With changes in de Broglie wavelength or grazing angle the relative diffraction intensities show significant variations which shed light on the nature of the atom-surface interaction potential. The observations are explained in terms of quantum reflection at the long-range attractive Casimir-van der Waals potential.



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496 - Bum Suk Zhao , Gerard Meijer , 2010
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Quantum reflection of thermal He atoms from various surfaces (glass slide, GaAs wafer, flat and structured Cr) at grazing conditions is studied within the elastic close-coupling formalism. Comparison with the experimental results of B.S. Zhao et al, Phys. Rev. Lett. {bf 105}, 133203 (2010) is quite reasonable but the conclusions of the present theoretical analysis are different from those discussed in the experimental work. The universal linear behavior observed in the dependence of the reflection probability on the incident wave vector component perpendicular to the surface is only valid at small values of the component whereas, at larger values, deviation from the linearity is evident, approaching a quadratic dependence at higher values. The surface roughness seems to play no important role in this scattering. Moreover, the claim that one observes a transition from quantum to classical reflection seems to be imprecise.
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