Mean excitation energies of Al, Ni, Se, Ag and Au extracted from alpha particle stopping power measurements

Abstract Stopping power measurements for alpha particles traversing targets of Al, Ni, Se, Ag and Au have been analyzed both with and without inclusion of a low velocity projectile- z 3 correction in the Bethe-Bloch formula in order to extract mean excitation energies. In the former case, the values obtained for Al and Ni are consistent with expectation, whereas those obtained for Se, Ag and Au lie 34%, 28% and 12%, respectively, above generally accepted values. Also, the method of analysis was modified by incorporation of an effective charge parameter while fixing mean excitation energies at the generally accepted values in order to include some stopping power measurements at energies below the limit of strict applicability of the Bethe-Bloch formula; the quality of fit to the data deteriorated for all targets except Ni.