Nuclear charge distribution in the region of symmetric fission of ²³⁸U by protons of energy 20–85 MeV

Abstract

Independent formation cross sections in the fission of 238U by protons of energy 20-85 MeV were obtained for the nuclides IllAg, 112Ag, "7In, 115111, IllPd, and "5Cd. The last three mentioned were estimated on the basis of measurements and isomeric yield data. Charge dispersion curves were constructed and Z,, the most probable charge, determined. The values for (ZA -Z,) lie intermediate between those measured for fission products of higher and lower mass. The number of neutrons emitted was estimated and found to be higher than in asymmetric fission, leading to the conclusion that the former are events arising from higher deposition energies.

Nuclear charge dispersion studies in the light-mass region formed in the fission of 238U by protons of energy 35–85 MeV

“…The precision on the resulting values of (ZA -Z,) and fwhm in Z units is, on the average, 3.5% and 8%, respectively, with the exception of the (2, -2,) value at 35 MeV which appears to be too low by -15%, this being probably attributable to poor precision on 76As and 7 8 A~ independent cross sections at that particular energy. The variation of (Z, -2,) and fwhm as a function of bombarding energy is shown in Figs. 4 and 5 respectively, along with data of several other workers (1,3,(5)(6)(7).…”

“…Both effects are found to be more pronounced in the heavy partner (1,4) than in the light one (3) when one considers the type of asymmetric mass split which is most probable ( Z = 55 and Z = 38 regions respectively). Symmetric mass divisions yield intermediate results so far as the rate of displacement of Z, is concerned (6). Recent results obtained show that in the case of very asymmetric fission, changes in Z,, are less sensitive to increases in incident energy and that only narrow charge distribution curves are compatible with the 'With financial assistance from the National Research Council of Canada.…”

“…In the 20-85 MeV range, the McGill group has produced a substantial body of experimental data, particularly for the proton fission of 238U (1)(2)(3)(4)(5)(6)(7). Charge dispersion curves have been found to be adequately represented by a Gaussian distribution.…”