Positional order and thermal expansion of surface crystalline N-alkane monolayers

The surface crystalline monolayer formed at the liquid-vapor interface of the n-alkene eicosane was studied using high resolution synchrotron grazing incidence X ray diffraction (GID) measurement. The diffraction peaks were found to be resolution limited indicating that the domain size is at least on the order of 1 micrometer. The temperature variation in the GID peak position was accurately measured. The coefficient of thermal expansion was found to be comparable to the coefficient measured in the bulk rotator phase.