Studies of observed trends in values of Bethe–Bloch parameters extracted from stopping power measurements

Abstract

AbstractIn the course of previous investigations, trends in values of the Bethe–Bloch parameters, mean excitation energy (I) and Barkas‐effect parameter (b), have been observed. Generally I values decrease with increasing projectile atomic number (z) whereas b values increase. However, the opposite trends have been previously observed for ZnSe and GaAs targets traversed by 1H and 4He projectiles. In the present study, that opposite trend was also followed when 7Li projectiles were included. When selected measurements for 4He, 12C, 14N, and 16O projectiles impinging on Si targets were analyzed, extracted I and b values followed essentially the original trends in z dependence. Stopping power measurements for 12 elemental targets with atomic numbers (Z) lying between 12 and 48 traversed by 29Si projectiles have been analyzed for determination of values of a single effective charge parameter, as part of a continuing study of systematics in such values in terms of both z and Z. Two other sets of measurements featuring 7Li projectiles and eight elemental targets with Z values between 5 and 48 have been similarly analyzed. In some of the effective charge studies the data proved amenable to extraction of three parameters, so that results could be included in the ongoing study of z dependences of extracted values of I and b. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004