Anisotropy of Fragments in the Neutron-Induced Fission of Pu240, Pu242, and Pu241

Abstract

Experimental data are presented for the angular distribution of fragments in the neutron-induced fission of ${\mathrm{Pu}}^{240}$ and ${\mathrm{Pu}}^{242}$, for a range of neutron energies from 0.65 to 8.25 MeV. The results are compared with other available data for even-even target isotopes by means of the parameter ${K_0}^2$. It is concluded that excitation energy alone is not sufficient to describe the ${K_0}^2$ values for this class of fissioning nuclei. A correlation between ${K_0}^2$ and fissionability is obtained. Comparison is also made with data for the even-odd target nuclei ${\mathrm{U}}^{235}$, ${\mathrm{U}}^{233}$, and ${\mathrm{Pu}}^{239}$. It is concluded that the correlation with fissionability shown by the even-even targets could well explain the major part of the "anomalous spin effect" shown by the even-odd nuclei. Data for the anisotropy of fragments in the fission of ${\mathrm{Pu}}^{241}$ are also recorded.