To observe specular oscillations in ion-surface scattering originating from layer-by-layer desorption of an electron stimulated desorbed (ESD) surface, a 15 keV proton beam was impinged on the surface with an angle of incidence less than 1°. We prepared an experimental system to examine the scattering yields of re‰ecting protons by conveniently employing a ‰uorescent screen to view scattering yields (scattering patterns) and a commercial digital camera for yield measurements. Because the present energy of the proton beam was too low to illuminate the screen, a micro-channel plate was inserted in front of the screen. Measurements with electron irradiation show obvious damping specular oscillations; the widths of angular distributions of scattered protons simultaneously oscillated with increasing electron ‰uence. From the measured periods of the oscillations, the ESD rates of thermal desorption from KBr(001) at 1.5 keV electrons irradiation were obtained for sample temperatures.

Desorption yields obtained from a KBr(001) surface irradiated by 1.5-3-keV electrons have been measured via layerby-layer mode removal. The yields are obtained from the inverse electron fluences required to remove the monolayer, which are measured from the specular intensity oscillations of 15-keV protons incident on the surface with small angles (≤1°). The desorption yield dependence on electron energy and beam current density (range : ≤100 nA cm-2) of the incident electrons has been measured while varying the sample temperature (350-470 K). The electron energy dependence is weak, and there is no apparent beam current density dependence. However, the initial half-period of the intensity oscillation curve tends to extend, and the oscillation shifts to higher electron fluence with increasing electron energy, electron beam current density, and decreasing sample temperature. A possible explanation for the aggregation is provided via attributing this result to the existence of aggregated F centers.