LOW-ENERGY NE-ADSORBED BE SURFACES( BOMBARDMENT ON O)

Time-of-flight (TOF) spectra of Be recoiled from clean and 0-adsorbed polycrystalline Be surfaces were measured for low-energy (less-than-or -equal-to 1 keV) Ne+ bombardment. Comparison of the TOF spectra for Be 0 (neutral Be) with those for Be0 + Be+ revealed that the Be+ fraction increases upon O-adsorption and that it is larger for surface-recoile d Be than for directly recoiled Be. It is suggested that the excitatio n of the Be 2s electron in the Be-Be collision plays an important role in the Be+ creation. The effect of 0 adsorption is possibly twofold. Be becomes positively charged by bonding to O, which facilitates creat ion of Be+ in the Be-Be collision. The decrease (increase) in neutrali zation (ionization) rates of Be+ (excited Be) along the outgoing traje ctory upon 0 adsorption also enhances the Be+ fraction.