Critical temperatures of two-dimensional condensation in monolayers of Ar, Kr, or Xe adsorbed on lamellar halides

Abstract

From sets of adsorption isotherms, critical temperatures of two-dimensional condensation have been determined for the first monolayer of Ar, Kr, or Xe adsorbed on a number of lamellar dihalides. Once properly scaled by the critical temperature of the bulk adsorbate, their value appears to be strikingly correlated to the so-called dimensional incompatibility between the adsorbate and the substrate. Their important variation (up to 40%) indicates a strong influence of the structure of the substrate on the properties of the monolayers, chiefly on those of the high density phase involved in the 2D condensation. Depending on the value of the so-called dimensional incompatibility, this phase takes on one of at least four different structures, ranging from liquidlike to lattice wise. Only in the first case does the theory give a good quantitative account of the experimental results. For the other types of structure, we present a qualitative analysis of the results, trying to single out the main factors responsible for the values taken by the critical temperatures as well as for their variation with the dimensional incompatibility.