Non-destructive quantum reflection of helium dimers and trimers from a plane ruled grating

Abstract

We report on non-destructive scattering and diffraction of He, He₂, and He₃ from a plane ruled reflection grating. At grazing incidence the normal component of the particle’s wave-vector is sufficiently small to allow for quantum reflection at the attractive Casimir-van der Waals particle–surface interaction potential. Quantum reflection occurs tens of nanometers in front of the surface, before the dimers and trimers reach the region where the surface-induced forces would inevitably cause breakup of the fragile bonds. The reflected particles are identified via their mass-dependent diffraction angles and by mass spectrometry. The intensity distributions of the observed diffraction patterns are discussed in terms of the grating’s blaze angle