Neutron Resonance Spectroscopy. XIII. Na to 320 keV

Abstract

Results are presented of measurements of the total cross section vs energy which was measured to 320 keV for pure metallic sodium. $R$-matrix fits were made to the seven prominent observed resonances. The best-fit parameters for ($E_0,\Gamma ,J,l$) for each resonance are: (2.850, 0.400, 1, 0); (53.15, 1.08, 2, 1); (199.0, 4.5, 1, 0); (212.5, 15, 0, 1); (238, 3.9, 2, 1); (242, 3.5, 0, 1); (297, 1.8, 2, 0), where $E_0$ and $\Gamma$ are in keV. Three levels are assigned to be $s$ levels, and four to be $p$ levels. This gives ${10}^4{S}_0=0.24\left(1_{-0.58\mathrm{}}^{+1.91\mathrm{}}\right)$ and ${10}^4{S}_1=2.06\left(1_{-0.39\mathrm{}}^{+0.77\mathrm{}}\right)$. The $S_1$ evaluation includes the presence of weak $p$ levels seen in capture measurements by others.