Commensurate-incommensurate and rotational transitions of monolayer xenon on single-crystal graphite

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 √3×√3R30^∘ 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.