MULTILAYER ADSORPTION OF NEON ON GRAPHITE

We used an ellipsometric technique to measure adsorption isotherms for neon on graphite over the temperature range from 11 to 24.6 K. Discre te layer condensation steps were observed from the second to as high a s the ninth layer. Chemical potentials at layer condensations and widt hs of the layer condensation steps were tabulated, and layer critical points were determined from the temperature dependence of the widths. Critical temperatures of the second and third layers are found to be 1 9.5 and 18.8 K respectively, in agreement with earlier work, but for l ayers 5, 6, and 7 increase to 21.8, 22.0, and 22.3 K respectively. Thi s suggests that the roughening temperature of the (111) facet of neon is near 22.3 K, rather than 19 K as previously supposed.