Relative Stopping Power of Some Metallic Elements for 28.7-MeV Protons

The stopping power of Be, Ti, V, Co, Ni, Cu, Ag, Ta, W, Ir, and Au were compared with Al at an average proton energy of 28.7 MeV. Accuracies of 0.25% were obtained by using a scattering foil and subsequent collimation to produce two identical beams. The energy and intensity were continually monitored in one beam. Comparisons were made in the other by rotating the samples to produce small changes in thickness. Anomalously high stopping powers were observed in the transition region where the $3d$ shell is being filled inside a completed $s$ shell.