Stopping power of Zr, Gd, and Ta for 5-12-MeV protons and deuterons. Further evidence of an oscillatory behavior of the excitation potential

The stopping power of Zr, Gd, and Ta for 5-12-MeV protons and deuterons was measured. The accuracy was 0.3% for Zr and Ta and 0.6% for Gd. The results are compared with Riso data published earlier and it is shown that the ratio between the mean excitation potential and the atomic number cannot be a monotonically decreasing function of the atomic number. An oscillatory dependence is suggested