Zero-order desorption is always observed in phase equilibrium within adsorbates?

Abstract

The zero-order desorption spectra are markedly well described by the desorption rate formula recently proposed by us. According to the formula the rate is proportional to the activity of adsorbates and the activity becomes constant independent of density when liquid-gas two-phase equilibrium occurs in an adsorbate layer. The zero-order desorption was also observed in another type of phase equilibrium, i.e., the phase equilibrium between adsorbate-induced-reconstructed and normally-adsorbed phases of the H/Ni(110) system. These two kinds of experimental findings of the zero-order desorption suggest that the zero-order desorption must generally be observed in any kind of phase equilibrium of first-order phase transitions. Taking this argument for granted, we can extract thermodynamic information about an adsorbate from conventional techniques of thermal or isothermal desorption experiments. As an example of such data analysis, the isothermal plot of chemical potential versus coverage is obtained from observed thermal desorption spectra.