Neutron Radiative Capture in Na, Al, Fe, and Ni from 1 to 200 keV

Neutron radiative capture in Na, Al, Fe, and Ni has been measured from 100 eV to 200 keV with a 1.25-m-diam liquid scintillator detector at the Rensselaer LINAC Laboratory. Radiation widths were determined for those resonances whose neutron widths are well known, while the resonance capture areas (${\sigma }_0{\Gamma }_{\gamma }$) were determined for most of the other resonances. Considerably more resonances were observed in the capture measurements upon Fe and Ni than had been observed in total cross-section measurements. It is reasonable to assign most if not all of these previously undetected resonances to $p$-wave neutrons, and from these data $p$-wave strength functions of (0.10±0.04) × ${10}^{-4\mathrm{}}$ and (0.04±0.03) × ${10}^{-4\mathrm{}}$ were determined, respectively, for ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$ and ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$. These strength functions are probably just upper limits to the true $p$-wave strength functions and are an order of magnitude smaller than optical-model predictions.