Surface melting of multilayer oxygen films on graphite studied by neutron diffraction

The results of a neutron-diffraction study of the melting properties of multilayer oxygen films are presented. The experiments have been carried out between 30 and 55 K on films ranging from 2 to 8 layers in thickness. A compound solid-liquid film is observed in the range 40–48 K. This composite film results from surface melting of the solid film phase which is present at 40 K. The thickness of its melted component is proportional to ln($T_t$-T), where $T_t$ is the melting temperature of bulk oxygen. The structure of its solid component is nearly identical to that of the bulk β phase. The data suggest that multiple wetting transitions may be present in this system.