Commensurate-incommensurate transition of monolayer krypton on graphite by helium-atom scattering

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Abstract
The commensurate-incommensurate transition of monolayer krypton films on a graphite single-crystal substrate is observed by helium-atom diffraction for transition temperatures in the range 50–60 K. The change in lattice spacing appears continuous, with an upper limit of 0.3% on a possible jump, with no detectable hysteresis. The slightly incommensurate phase is disordered but apparently well correlated. The spatial correlation length changes in a possibly discontinuous manner. A decrease of specular and diffracted intensities while the film is still commensurate is observed. This may be due to incoherent elastic scattering from isolated defects, or possibly to increased inelastic scattering.