On the appearance threshold and the reverse motion of ions in electron-stimulated desorption

We report here the first observation of the ESD appearance threshold energy exceeding the energy of the inner shell ionization, which is interpreted as a consequence of a shake-off process. For a tightly bound chemisorbed system we discovered the possibility of reverse ion motion due to an interatomic Auger process. The observed expansion of the ion retardation curves and the weakening of the isotope effect in the case of reverse ion motion is discussed in terms of an improved ESD model considering local surface field relaxation.