Commensurate, incommensurate and rotated Xe monolayers on Pt(111): A He diffraction study

Commensurate, incommensurate, and incommensurate-rotated Xe monolayers are shown to exist on Pt(111), i.e., on a close-packed ``smooth'' metal surface. The existence of a commensurate-incommensurate transition induced by varying temperature at constant coverage is experimentally demonstrated (TIC=57--59 K). The use of high-resolution He diffraction enables the investigation of structures and transitions of 2D phases irrespective of the nature of the substrate and without any damaging of the adsorbed phase.