Stopping Powers of Some Solids for 30-90-MeVU238Ions

Uranium ions of energies in the range 30-90 MeV from the Oak Ridge Tandem accelerator were used to measure stopping powers for C, Al, Ni, Ag, and Au foils. Foil thicknesses were determined by $\alpha$-particle energy-loss measurements. The results are compared with various theoretical predictions. Subtraction of an assumed nuclear-stopping component leaves a residual electronic stopping power which is velocity proportional but does not appear to extrapolate to the origin, in disagreement with theory. Comparisons with other ions indicate that heavier ions exhibit larger discrepancies with theory in that the velocity-proportional stopping extrapolates to zero stopping at larger values of velocity.