Scale factors for neutron diffraction and neutron inelastic scattering are presented for common adsorbates, and the feasibility of experiments is discussed together with the information gained by each type of experiment. Diffraction, coherent inelastic scattering, and incoherent scattering are treated separately. Studies of monolayers of 36Ar adsorbed on grafoil show that argon forms almost ideal two-dimensional crystals, which are incommensurate with the substrate. The incommensurability gives, however, rise to a distortion of the lattice. Studies of 4He on grafoil reveal that bulklike rotons exist in films of only a few atomic layers thickness.
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