Values of modified Bethe–Bloch stopping power parameters for polysulfone extracted from stopping power measurements with light projectiles

Abstract

Recent measurements of the stopping powers of polysulfone for 0.66–1.74 MeV protons and 1.04–3.20 MeV alpha particles have been analyzed in terms of the modified Bethe–Bloch theory in order to extract values of the parameters characterizing the formalism utilized. Resulting values of mean excitation energy ( I) and Barkas-effect parameter ( b), respectively, were 83.3 eV and 1.05 for proton data, and 81.1 eV and 1.38 for alpha particle data. The lower energy alpha particle data were included by employing a single effective charge parameter ( λ) evaluated at 1.63. The composite weighted value of mean excitation energy, 82.9 eV, lies some 6% above the additivity-based estimate, whereas the corresponding value of Barkas-effect parameter, 1.22, agrees quite well with the prescribed interval of 1.4±0.1.