Abstract
Fractional independent or cumulative chain yields of 35 fission products were determined for the photofission of with 20-MeV bremsstrahlung, using direct spectrometry of irradiated uranium samples, -ray spectrometry of fission product catcher foils, and chemical sparation techniques. For the mass chains 131-136 the width parameter of the charge distribution was obtained. An average value of 0.93 ± 0.06 was deduced for . A comparison of this value with the results for other low-energy fissioning systems indicates that the width of the charge distribution is practically independent of the excitation energy of the compound nucleus. Using the average value, the most probable charges (20 MeV) were calculated for 8 light and 12 heavy mass chains. A comparison of the deduced (20 MeV) behavior with the expectations of the unchanged charge density hypothesis shows the higher charge-to-mass ratio of the light fragments compared to the heavy ones and the influence of the closed 50-proton shell on the charge distribution. The (20 MeV) values determined are very well reproduced by the empirical relation of Nethaway except in the vicinity of the line.
NUCLEAR REACTIONS, FISSION , MeV; measured: fragment -ray spectra; deduced: charge distributions, width and most probable charges.
- Received 27 August 1979
DOI:https://doi.org/10.1103/PhysRevC.21.629
©1980 American Physical Society