UC Riverside

The absolute ionization probability of energetic ( > 500 eV) particles recoiled from Al(100) by 2 and 5 keV Xe+ bombardment was measured with time-of-flight spectroscopy. These values were then used to calibrate the energy and angular distributions of low-energy (10-600 eV) sputtered ions collected with an electrostatic analyzer. The independent-particle model of nonadiabatic surface-atom charge exchange, which is typically used to analyze single scattering events, was applied to the ion fractions of the recoiled and sputtered atoms. The model describes all the experimental data from a few eV to the keV range if a different surface electronic temperature is used for recoiling and sputtering. This suggests that the ionization process depends on the instantaneous surface condition at the time of ion emission.