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 Å) deteriorates to less than 100 Å, 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.

• Received 29 January 1981

DOI:https://doi.org/10.1103/PhysRevLett.46.1533