The Total Neutron Cross Section of Nitrogen

The total cross section of nitrogen has been measured for neutrons in the energy range 200 to 1800 kev, using scatterers of liquid nitrogen and of lithium azide. Eleven resonances were found, corresponding to excited states in the compound nucleus ${\mathrm{N}}^{15}$, with natural widths of from 3 to 54 kev. Nine of these can be identified with resonances previously known in the reactions ${\mathrm{N}}^{14}\mathrm{}(n,p)\mathrm{}{\mathrm{C}}^{14}$, ${\mathrm{N}}^{14}(n,\alpha ){\mathrm{B}}^{11}$ or ${\mathrm{C}}^{14}\mathrm{}(p,n)\mathrm{}{\mathrm{N}}^{14}$. From a comparison of the measured and computed elastic scattering cross sections, $J$-values can be assigned to most of the observed states. In some cases the parity also can be determined and the effective level spacing $D_J$ computed for decay by neutron, proton, or $\alpha$-particle emission. At least for proton emission, it must be concluded that the quantities $D_J$, which contain implicitly the matrix elements for the transition, can vary by a factor of at least 100.