Total Neutron Cross Sections of Helium, Neon, Argon, Krypton, and Xenon

Abstract

The total neutron cross sections of the noble gases helium, neon, argon, krypton, and xenon have been measured for neutron energies from 120 kev to 6.2 Mev and from 12.1 Mev to 19.8 Mev by a transmission experiment. The neutrons were produced using the ${\mathrm{Li}}^7(p, n){\mathrm{Be}}^7$, the $\mathrm{T}(p, n){\mathrm{He}}^3$, the $\mathrm{D}(d, n){\mathrm{He}}^3$, and the $\mathrm{T}(d, n){\mathrm{He}}^4$ reactions in the appropriate energy intervals. A Van de Graaff accelerator was the source of the protons or deuterons. In general, the results obtained agree with previous work where such work exists. A previously unobserved $S$-wave scattering resonance was found in neon at about 500 kev, indicating the presence of an excited state in ${\mathrm{Ne}}^{21}$ with $J=\frac{1}{2}$ and even parity. The results for argon, krypton, and xenon exhibit general agreement with the cross sections of neighboring elements, as would be expected from the previously observed smooth variation of the $\sigma (A, E)$ surface.