Neutron binding energy

From these various processes, one can separate at least three simple prototype pathways whereby the compound nucleus may get rid of its several million electron volts which constitute the neutron binding energy. These should encompass essentially all other possibilities, as far as chemical... 

Figure 11.7 Schematic diagram of neutron, fission, and 7-ray widths of a typical nucleus with a neutron binding energy slightly less than 6 MeV. The inset shows the predicted fission excitation function for a nucleus with Bf — Bn = 0.75 MeV together with more recent data.

Fission, A(n, f), which is most likely at thermal energies but occurs at all energies where the neutron binding energy exceeds the fission barrier height for fissile nuclei. 

Na has larger neutron binding energy, Sn, than any lighter odd-A nucleus. 

Al and 39 K have the largest neutron binding energies, Sn, of any stable odd-A nuclei (with 39K winning by a mere 0.03 MeV). 

IV has a larger neutron binding energy than any heather odd-A nucleus, a consequence of its magic number N = 28 neutrons. It is one of jive elements (Ca, Ti, V, Cr, and Fe) having a stable isotope with 28 neutrons, a record exceeded only by N = 82 neutrons. 

SyZn has the lowest neutron binding energy of any stable nucleus after 21Ne. This is a manifestation of the general decline in binding energies above the iron abundance peak. 

For the use of nuclides as nuclear fuel, their fissionability is the most important aspect. High fission yields by thermal neutrons are obtained if the binding energy of an additional neutron is higher than the fission barrier. Fission barriers, neutron binding energies and fission cross sections are listed for some nuclides in Table 11.1. The fission cross sections are high for and Pu, as already mentioned in... 

Figure 14.11. Logarithm of the ratio of the cross sections (Tn,f and for various nuclides of the actinides as a function of the difference between the neutron binding energy B(n) and the energy barrier of fission E. (According to G. T. Seaborg The Transuranium Elements. Yale University Press 1958 Addison-Wesley Publ. Comp, Reading, Mass., S, 166/167 S. 240/241.)...

The energy released is the (neutron) binding energy of the nucleus g. The total energy of the nucleus has thus decreased as is indicated in Figure 11.1(B) it is common to refer to this decrease as a potential well. The nucleons can be considered to occupy different levels in such a potential well. The exact shape of the well is uncertain (parabolic, square, etc.) and depends on the mathematical form assumed for the interaction between the incoming particle and the nucleus. 

Only reactions in which particle widths are known are listed and not all resonances are included. The radiation widths are for thermal neutron capture at an excitation equal to the neutron binding energy. The figures are taken mainly from references [15], [24] and [32]. 

Sufficient Be (4 10 gm) can be produced by cyclotron bombardments to enable reaction cross sections to be measured. Hanna found a cross section of (5-3 0.8) X10 cm for the Be (np) reaction with thermal neutrons and a cross section of less than 10 cm for the (ncc) reaction. These results are consistent with odd parity for Be". Comparison with the cross section for the inverse reaction Li (pn) suggests an odd parity level near the neutron binding energy in Be . 

Energy balance in deuteron reactions. In most nuclear reactions in which the deuteron is the incident particle, the energy balance is favourable. In the [d, p) reaction the deuteron acts as a vehicle for the conveyance of a neutron the ( -value therefore is equal to the neutron binding energy of the product nucleus less the binding energy of the deuteron ... 

Table 3- Neutron binding energies, from [d, p), [d, t), (y, n) and n, y) reactions in Mev. Figures in parantheses show errors beyond the decimal point letters, to references at the end...

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