Heat-capacity measurements of ethylene on graphite in both the submonolayer and monolayer regions reveal a weak and broad anomaly relating to the melting transition of the overlayer. The findings in the submonolayer are in contrast to all previous studies in physisorbed systems, where sharp heat-capacity signals were observed. These results suggest that the melting of ethylene on graphite is a continuous transition for submonolayer as well as monolayer coverages.

• Received 7 October 1985

DOI:https://doi.org/10.1103/PhysRevLett.56.1579