CHARGE-STATE DEPENDENCE OF THE STOPPING POWER OF 1 MEV A NI-58 IONS/

The dependence of the energy loss of 60 MeV Ni-58 ions on the incident and analysed charge state was measured in thin carbon foils with a Q3 D magnetic spectrograph. The surface contamination of the carbon foils was determined by elastic scattering of 12 MeV protons and included i n the analysis of the energy loss data. Five incident charge states be tween q(in) = 8+ and q(in) = 18+ were selected. A reduction of the sto pping power in the first few atomic layers is observed for low inciden t charge states and an enhancement for high ones with the transition o ccurring at q(in) approximate to 13.5. The results are discussed in te rms of a reduction of the dynamic screening of the effective charge of the projectiles at the target surface.