Effects of the projectile electronic structure on stopping parameters for nickel

Abstract

The stopping powers of nickel foils for 1H+, 2H+ and 4He2+ ions have been accurately measured over the energy range E≈(0.166−2.725)MeV/amu. The data were compared to those reported in the literature and to values derived by the SRIM-2003 code. They were analysed in the framework of the modified Bethe–Bloch theory to extract the target mean excitation and ionisation potential, I, and the Barkas effect parameter, b. The values derived from the proton and the alpha particle data are {I=(311.11±2.61)eV, b=1.38±0.01} and {I=(276.12±2.84)eV, b=1.58±0.01}, respectively. They thus show opposite variations of the I and b parameters as the projectile charge increases, presumably due only to the incident ions electronic structure. Besides, the reduced stopping power data for incident deuterons show to be fully consistent with those for protons indicating no effect of the projectile isotopic structure on the target stopping parameters. These results are discussed in comparison with ones reported in the literature.