Thin (thickness $h\approx 3\mathrm{nm})$ films of n-octadecane and n-hexadecane adsorbed on mica surfaces from vapor close to their bulk melting points ${(T}_m)$ have been studied in a surface force apparatus. Using data on the growth rate of capillary condensates between the mica surfaces in contact and measurements of h, we have identified a transition in the structure of the adsorbed films a few degrees above $T_m.$ As T decreases the alkane layers appear to undergo a transition to a more ordered structure, akin to the postulated “surface freezing” of long-chain liquid n-alkanes.

• Received 12 November 1999

DOI:https://doi.org/10.1103/PhysRevE.61.7239