Synchrotron X-Ray Study of the Commensurate-Incommensurate Transition of Monolayer Krypton on Graphite

We report a high-resolution synchrotron x-ray scattering study of the commensurateto-incommensurate transition of monolayer krypton physisorbed on $\mathrm{ZYX}$ graphite. At the transition the substrate-limited coherence of the commensurate monolayer (2300 \AA{}) deteriorates to less than 100 \AA{}, demonstrating that atomic positional disorder is a dominant feature of the weakly incommensurate system. The peak position follows a $\frac{1}{3}$ power law versus reduced temperature.