Energy Loss and Straggling of Alpha Particles in Metal Foils

The energy loss and energy straggling of charged particles in foils of aluminum, nickel, silver, and gold have been studied as a function of total material thickness and of particle energy using 8.78 MeV Th $C^{\prime }$ alpha particles and solid-state detectors. Energy thickness, stopping power, and straggling cruves were obtained. The straggling results are compared with theoretical predictions of Bohr, Bethe, and Livingston, and of Titeica. Large discrepancies are found at low energy. Foil inhomogeneities and multiple scattering will probably not account fully for these. It is suggested that the effects of capture and loss of electrons, and the fluctuations of charge exchange are primarily responsible.