[en] A recent study by the author of effective charge parameterization of electronic stopping powers for heavy ions has indicated a necessity for two such parameters. The behavior of each of the selected parameters as a function of projectile atomic number (z) for a fixed target atomic number (Z) suggests structure, with a dominant maximum occurring near z = 14 and a lesser maximum appearing near z = 26 in the cases of C, Al, and Cu targets. This trend is not apparent for the case of Ag targets, however. The consequence of this structure on the effective charge is investigated. The results are related to those of previous studies of z-oscillations in the stopping power of a given target. Conjectural interpretation of parameter structure in terms of atomic shell configurations is advanced. 9 refs., 17 figs

[en] Values of the parameters of the modified Bethe-Bloch theory have been ascertained for kapton by analyzing recent measurements of stopping powers for 0.56--1.54-MeV protons and 1.08--3.19-MeV alpha particles. The resulting recommended values of the target parameters are 80.1 eV for mean excitation energy and 1.64 for the Barkas-effect parameter and 1.86 for a single effective-charge parameter assigned to the kapton-alpha particle target-projectile combination

[en] Recent transmission-type measurements of the stopping powers of Vyns (a vinylchloride-vinylacetate copolymer) for 0.55-1.75 MeV protons and 1.03-3.22 MeV alpha particles have been analyzed in terms of modified Bethe-Bloch stopping power theory in order to extract values of the parameters known as the mean excitation energy (I) and Barkas-effect parameter (b). The weighted average value of I thus established, 110.8 eV, exceeds the prediction based on linear additivity by some 3%, and the weighted average of b, 1.54, agrees very well with expectations. The results of this analysis are compared with those from a previous similar study of another material having essentially the same average atomic number and atomic weight but quite different atomic composition, called Kapton

[en] One version of modified Bethe-Bloch stopping power theory features two parameters characteristic of the target material, the mean excitation energy and the Barkas-effect parameter, that can be evaluated through fits to accurate stopping power measurements. In several recent investigations, the values of these parameters thus determined have revealed a dependence on projectile atomic number. Most of those studies have featured target materials possessing aggregation effects, such as solid compounds and alloys. In the current investigation, the search for systematics in projectile-z dependence has been extended to encompass other target materials, including elemental targets. Most of the results are corroborative of the previously reported trends

[en] 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-z³ 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. (Auth.)

[en] Mean excitation energies for Si, Ni, Ge, Y, Ag, and Au have been extracted from previous stopping power measurements with alpha particle projectiles. Data were analyzed both with and without inclusion of the low-velocity projectile-z³ effect. Values of mean excitation energy obtained by the former method proved consistent with generally accepted values for Si, Ge, and Y, but lay higher than expected for Ni, Ag, and Au by about 11%, 20%, and 20%, respectively. (Auth.)

[en] Modified Bethe-Bloch stopping power theory permits fairly accurate calculation of energy losses over a broad interval of projectile velocity v = νc insofar as several parameters appearing in the revised Bethe-Bloch formula have been corectly evaluated. Since the parameters cannot in general be ascertained by calculation from first principles, fits of theory to measurement remain the best method of evaluation. The parameters alluded to are: the target mean excitation energy; the shell correction scaling parameters; the composite single free parameter of the Barkas (projectile-z₃) effect correction formalism, and the strength of the correction term; the high velocity density effect correction parameter; and the low velocity charge state parameter. These parameters are discussed

[en] 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

[en] Recently reported measurements of the stopping power of Al₂O₃ for 0.90-2.50 MeV protons and deuterons have been analyzed in terms of modified Bethe-Bloch theory. Values of the mean excitation energy (I) and Barkas-effect parameter (b) have been extracted from the data, yielding results for I and b, respectively, of 176.8 eV and 0.83 for protons, and of 182.7 eV and 1.02 for deuterons. These values of I exceed the additivity-based value by 32% for proton data and by 36% for deuteron data. Moreover, both extracted values of b lie well below the expected interval of 1.3-1.5

[en] Accurate measurements of the stopping powers of Al, Cu, Ag, and Au for protons, α particles, and Li ions have been analyzed to extract values of mean excitation energy (I) and Barkas-effect parameter (b) for each target material. Two versions of shell corrections were employed, with only one yielding consistent, plausible results. Recommended values of I and b for Al, Cu, and Ag are, respectively, 165 +/- 3 eV and 1.37 +/- 0.05, 329 +/- 4 eV and 1.36 +/- 0.06, and 483 +/- 5 eV and 1.30 +/- 0.07