Secondary-ion yields have been measured for Si and SiO2 targets bombarded by C, Si, Ge, and Ag projectiles over an energy range beween 0.4 and 10 MeV, where the atomic-collision process changes from a nuclear to an electronic one. Obtained yields of secondary Siq+ (q=1,2,3,4) ions for the C projectiles are generally decreasing functions of incident energy. On the other hand, the yields for Ag increase with increasing energy except for Si+. The possibility of multiple-charged recoil-ion production through the simultaneous process of ionization and recoil caused by the projectiles is discussed on the basis of an independent-electron model, which describes multiple ionization of atoms by energetic heavy-ion impact. © 1995 The American Physical Society.
