Mean excitation energies extracted from stopping power measurements of protons in polymers by using the modified Bethe-Bloch formula

Recent stopping power measurements in thin polymeric films have been performed for protons of 0.4-3.5 MeV energies using the indirect transmission technique [H. Ammi, S. Mammeri, M. Chekirine, B. Bouzid, M. Allab, Nucl. Instr. and Meth. B 198 (2002) 5]. Experimental stopping data have been analyzed with the modified Bethe-Bloch formula and the mean excitation energies I have been then extracted from the data. Resulting values for each thin film are 76 ± 1 eV in Mylar, 70.8 ± 1 eV in Makrofol, 82.2 ± 1.2 eV in LR-115 and 55.4 ± 1 eV in Polypropylene. The I-extracted values are compared to those IB calculated by using the Bragg's rule.