Resonance Scattering of Slow Neutrons on Indium

Abstract

The scattering of slow neutrons by indium was observed by using a crystal spectrometer as a monoenergetic neutron source. Thin scattering samples were placed in the neutron beam with the plane of the samples at a small angle to the incident beam. The samples therefore appeared thick for the transmitted neutrons but thin for neutrons scattered at right angles to the direction of the incident beam. A measurement of the scattered and the transmitted neutrons gives $\frac{{\sigma }_s}{{\sigma }_t}$. The total cross section ${\sigma }_t$ was also measured in the energy range from 0.3 to 11 ev and the value of ${\sigma }_s$ then computed. Both the total cross section and $\frac{{\sigma }_s}{{\sigma }_t}$ results could be well matched to the Breit-Wigner formulas from 0.3 to 3 ev with the same set of parameters, assuming that the spin of the compound state in ${\mathrm{In}}^{116}$ for the 1.456-ev level was 5. No determination of the spin state of the compound nucleus could be made for higher levels.