We have studied the structures and transitions of high-density xenon monolayers on single-crystal graphite using high-resolution synchrotron x-ray diffraction techniques. In contrast to the previous x-ray experiment, we find that at low temperatures, the xenon has a commensurate $\sqrt{3}\times \sqrt{3}R30°$ structure for a broad range of coverages. With decreasing temperature the novel reentrant sequence: aligned→rotated→aligned, occurs; this sequence is followed by a first-order incommensurate-commensurate transition.

• Received 27 May 1987

DOI:https://doi.org/10.1103/PhysRevB.36.7311