Field Desorption of Carbon Monoxide from Tungsten

Abstract

The field desorption of CO from tungsten has been investigated at three coverage intervals, corresponding to heats of adsorption of 0.7, 1.90, and 3.30 eV, respectively. Potential‐energy curves of adsorption have been obtained for these cases which seem to correspond to different binding states of CO on tungsten. Polarization corrections have relatively little effect on the shape of the curves but do shift them outward by small amounts. General agreement with the theory of field desorption proposed previously seems to hold and could be confirmed, in particular, for the energetics of desorption and for adsorbate tunneling. The discrepancy between the calculated values of the pre‐exponential terms of the desorption rate constant and the very low values found experimentally at low temperature in this and other cases seems to have no simple explanation and is blamed on entropy effects. The general reasonableness of the potential curves and that of the CO–W spacings obtained indicates that the ion—metal interaction can be expressed by an image potential to distances of the order of 2 Å.