We report the results of a high-resolution synchrotron x-ray–scattering study of the melting of Xe monolayers adsorbed on Ag(111). We find that at high temperatures (T>100 K) all features of the melting transition are, within errors, the same as those found for xenon on graphite. Specifically, in both cases the xenon solid melts into a ‘‘hexatic phase’’ with essentially identical hexatic stiffness. This strongly suggests that the existence of the hexatic phase is a feature of the two-dimensional melting process rather than the adsorbate-substrate interaction.

• Received 10 June 1987

DOI:https://doi.org/10.1103/PhysRevLett.59.1706