Measurements of the mean energy-loss of swift heavy ions in carbon with high precision

Z(I) dependent effects in heavy ion stopping around stopping maximum under conditions of equilibrium charge have been measured with a time of flight-energy elastic recoil detection analysis (ToF-E ERDA) set-up. The ToF section was used to tag individual recoil atoms with their energy prior to entering the stopping foil and the exit energy was measured subsequently using a Si p-i-n charged particle detector. The mean energy-loss and average energy of recoils have been determined for many elements with Z(I) = 3-26 in a continuous energy range from similar to0.2 to similar to0.9 MeV per nucleon and from similar to0.03 to 0.1 MeV per nucleon for Au-79. The stopping power and energy dependence were in good agreement with most literature data. However. considerable discrepancies in the energy dependence were observed with semi-empirical SRIM-2000 estimates around the stopping power maximum fur some of the elements. This technique, which allows direct measurement of Z(I) effects in stopping foils to be performed with high-precision, showed that the dependence of the experimentally determined stopping number (L-exp) with the stopping parameter xi clustered around a trend line with Z(I) dependent deviations that exceeded the estimated uncertainty. The deviations were more significant for large xi and were 15%, between Be-9 and Li-9 at xi = 10. (C) 2001 Elsevier Science B.V. All rights reserved.