First-order corrections in modulated molecular beam desorption experiments

Rate constants for the desorption of molecules from surfaces can be readily measured using a combination of molecular-beam techniques and a surface-sensitive coverage probe such as time-resolved high-resolution electron-energy-loss spectroscopy (TREELS). The coverage dependence of the desorption rate is determined by establishing a steady-state coverage and then perturbing this equilibrium slightly with a pulsed or chopped molecular beam. This paper demonstrates that the correct interpretation of these measurements must take into account the influence of the modulation on the steady-state adsorbate concentration. This approach is used to analyze TREELS data for the desorption of CO from Cu(111).