Emission of Highly-Charged Ions from Solid Bombarded by Energetic Heavy Io

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The aim of the present study is to produce low-energy highly-charged ions with low momentum dispersion. For the purpose, we bombarded solid surface with energetic heavy ions and measured the yields of various secondary ions.In an energy range below several tens keV, particles are sputtered efficiently from solid target but few particles are charged. The sputtering is caused by cascade elastic collisions. In a MeV energy range, however, inelastic collision overcones the elastic collision and atoms in the target are ionized. If the ionized atoms on. an outermost atomic layer are recoiled by other low-energy secondary atoms, they probably carry charges and move slowly. Therefore, we measured systematically the yields of secondary charged particles as a function of incident energy of heavy ions. Used targets were metallic ones such as C. Al, Ti, Ni, Cu, Ho, W and Au, and an insu ator Al_2O_3. Incident partilces were-C, Si and Ge ions. The following conclusions are obtained :1. Singly-charged ions are. produced by the elastic cascade collision. their yield decreases. monotonically with increasing energy.2. The yields of highly-charged secondary ions increase at first and then decrease with energy. The maximun yields are at energies where the elastic and inelastic collisions compete.3. Other than atomic ions, various cluster ions are observed. The yields decrease monotonically and then increase with energy at the energy range where the inelastic collision is predominant.