Correlation Field, Two‐Dimensional First Order Phase Transition and Heats of Adsorption in CO₂on the NaCl(100) Cleavage Plane

Abstract

Adsorption 1 Molecular Structure / Phase Transitions 1 Spectroscopy, Infrared Infrared spectra of 13C1602 adsorbed on the NaCl(100) cleavage plane from zero to monolayer coverage 0 and the corresponding adsorption isotherms have been measured. At 0.3 Q , 6 Q 6 Q, , 0, being the C 0 2 monolayer coverage, the vj vibrational band of adsorbed COz shows a doublet structure due to a correlation field, whereas at Q 5 0.3 0, a single band is observed. -The coverage and polarization dependence of the spectra as well as the shape of the isotherms between 80 and 95 K adsorbate temperature reveal a two-dimensional (2D) first order phase transition from a 2D low density phase into a 2D island-like solid. The isosteric heats of adsorption have been determined to be 28.5 kJ rno1-l and 24 kJ mol-' (-10% and +25% error) for Q = 0.08 Qm and Q = 0.96 Q , , respectively. -In the 2D