Calculation of the Spin- and Energy-Dependent Fission Widths for 233U, 235U, 239Pu and 241Pu from Channel Theory

摘要

The spin- and energy-dependence of the fission widths are estimated for 233U, 235U, 239Pu and 241Pu from the channel theory of nuclear fission. The spin-dependent fission widths are deduced, by assuming the appropriate transition state spectrum, and the fission and capture cross sections are calculated with these fission widths. The results thus derived agree well with the experimental data which differ distinctively from nuclide to nuclide, and this is despite closely similar transition state spectra assumed for the different nuclides. This fact supports the validity of the spin-dependent fission widths derived from channel theory. The ratio Γf(I-1/2)/Γf(I+1/2) for the states due to s-wave neutrons are as follows: 2.5 for 233U, 1.8 for 235U, between 74 and 210 for 239Pu and 2.4 for 241Pu. The fission widths of 239Pu are thus seen to have exceptionally strong spin-dependence compared with the other nuclides.