Energy Straggling of Alpha Particles through Gases

Abstract

Measurements of the energy straggling of $\alpha$ particles through helium, air, argon, krypton, and xenon have been made for incident $\alpha$ energies between 2 and 4 MeV. These measurements were compared with the theoretical results of Bohr, Lewis, and Titeica. None of these theories gives satisfactory fits to the data, giving at best predictions within an order of magnitude of the experimental results. Capture and loss of electrons is a significant effect at these energies. The neglect of this effect and of the exact energy shell corrections, rather than an average shell correction, is believed to be the reason for the failure of these theories. Values of the stopping power for the $\alpha$ particles were also obtained. These were found to be in good agreement with proton energy-loss measurements after the usual corrections for mass and charge differences were made.