X-Ray diffraction from layers of n-alkanes adsorbed on graphite

The structure of 1 to 80 layers of C 16 H 34 and C 17 H 36 n-alkanes adsorbed on graphite has been studied as a function of temperature using synchrotron X-ray radiation. The measurements confirm that a surface phase of two to four layers, distinct from the bulk adsorbed on the graphite, is formed at room temperature. The structure of the subsequent layers, for a particular hydrocarbon, is not appreciably affected by the number of layers. Warren-like peaks are observed for the adsorbed phase and can be indexed in a centred oblique two-dimensional lattice.