High-energy recoil-ion emission in keV heavy-ion surface collisions

For keV Xe+, Kr+ and Ar+ ions incident at 30 degrees on Cu(110) we have observed the emission of negatively charged particles with energies up to about 40% of the primary energy. Bq. time-of-flight techniques we have found that electrons are emitted with energies : up to 80 eV. whereas the negatively charged high-energy. particles are Cu-recoil ions, High-energy Cu I ions have also been found. Simple energy and momentum conservation arguments show that such high recoil energies are indeed possible for multiple collision events in which the primary recoil ion scatters off one or more Cu atoms. (C) 1997 Elsevier Science B.V.