The Energy Dependence of the Resonant Scattering of Slow Neutrons from Gold

Abstract

The energy dependence of slow neutrons scattered from a thick gold target has been measured using a newly developed scattering chamber in conjunction with the Columbia slow neutron velocity spectrometer. A method of analysis has been developed for determining the ratio of the scattering cross section to the total cross section, $\frac{{\sigma }_s}{{\sigma }_t}$, as a function of energy for an "unknown" sample in terms of a calibration target for which $\left(\frac{{\sigma }_s}{{\sigma }_t}\right)\left(E\right)\mathrm{}$ is known. The agreement between the experimental determination of $\left(\frac{{\sigma }_s}{{\sigma }_t}\right)\left(E\right)\mathrm{}$ for gold in the energy range 0.7 to 8 ev and the Breit-Wigner theory is excellent. All the level parameters can be evaluated by combining these scattering data with the results of transmission experiments and the cross section for self-indication. The final results for the 4.9-ev gold level are: $J=1\mathrm{}$, $\Gamma =0.172\mathrm{}$ ev, ${\Gamma }_N=0.0211\mathrm{}$ ev, $R_{J=1\mathrm{}}=1.03\mathrm{}$ ${\mathrm{barn}}^{\mathrm{½}}$, $R_{J=2\mathrm{}}=0.917\mathrm{}$ ${\mathrm{barn}}^{\mathrm{½}}$.