Lattice-gas virial coefficients from isothermal desorption measurements: CO on Cu(001) and Cu(011)

We present an analysis technique for understanding coverage- and temperature-dependent desorption phenomena. Using a quasiequilibrium model, we derive an expression for the desorption rate in terms of a lattice-gas virial expansion and apply the results to CO desorption from Cu(001) and Cu(011). The interplay between short-range repulsion and long-range attraction leads to the vanishing of virial coefficients at some temperature and thus to a nearly coverage-independent desorption rate. The origin of kinetic compensation is shown in a simple statistical thermodynamic treatment of the adsorbed layer.