Triple-point wetting of multilayer films physisorbed on graphite

A graphite fiber microbalance technique is used to study the growth mode of Kr, Xe, ${\mathrm{CH}}_4$, and CO films on graphite. The maximum thickness of the adsorbed film is finite below the triple points ${\mathit{T}}_{\mathit{t}}$ of each of these adsorbates. The maximum thickness increases rapidly as T is brought toward ${\mathit{T}}_{\mathit{t}}$ and levels off for T≥${\mathit{T}}_{\mathit{t}}$. This behavior is suggestive of a wetting transition that is pinned at the respective ${\mathit{T}}_{\mathit{t}}$ of the adsorbates.