MULTIPLE NEUTRON CAPTURE IN THE MIKE FUSION EXPLOSION

Abstract

The constant ratio of yields of successive even or odd mass number nuclides produced in the Mike fusion explosion of 1952 implies an approximate constancy of the corresponding neutron capture cross sections for neutrons near 100 kev for the nuclei between U238 and U254. A discussion is given of the physical quantities on which the neutron capture cross sections depend, particularly radiation widths, nuclear level spacings, and neutron binding energies. It is concluded that conventional mass formulas are probably wrong in predicting a large decrease in neutron binding energy as one goes from U238 to U254. It is possible that the addition of a direct symmetry term to the mass formula might repair this difficulty. Another possibility is that an extra diffuseness of the nuclear surface in neutron-rich nuclei would reduce the Coulomb energy of the nucleus, thus stabilizing neutron binding energies.