Theory of Delayed-Neutron Physics

At least 38 of the fission product isotopes are now known to be delayed-neutron precursors. The region of delay ed-neutr on emission for each fission product element is predicted successfully by recent mass formulas, and the neutron emission probability (P_n) can be approximately related to basic nuclear parameters. Using P_n values and calculated cumulative fission yields, it is possible to account for some features of gross delayed-neutron emission from various types of fission. Further significant progress in understanding delayed-neutron emission is expected in the near future when spectroscopic studies are made on delayed-neutron precursors.