Some Cross-Section Limits for the Occurrence of the (n,He3) Reaction at 14.5 Mev

The ($n$, ${\mathrm{He}}^3$) reaction at 14.5±0.9 Mev has been investigated carefully with scintillation spectroscopy and radiochemical techniques. No case of an ($n$, ${\mathrm{He}}^3$) reaction could be detected at this energy. Upper limits were set on the ($n$, ${\mathrm{He}}^3$) cross section for the following target nuclides: ${\mathrm{Mg}}^{26}$(3.0), ${\mathrm{Al}}^{27}$(0.70), ${\mathrm{P}}^{31}$(0.25), ${\mathrm{K}}^{41}$(2.5), ${\mathrm{V}}^{51}$(0.33), ${\mathrm{Mn}}^{55}$(0.42), ${\mathrm{Co}}^{59}$(0.10), ${\mathrm{Cu}}^{63}$(0.08), ${\mathrm{As}}^{75}$(0.51), ${\mathrm{Zr}}^{94}$(0.4), ${\mathrm{Rh}}^{103}$(0.09), and ${\mathrm{Cs}}^{133}$(0.15), where the value in parentheses is the upper limit in millibarns. One case of the ($n, n^{\prime }\alpha$) reaction was detected at this energy, on ${\mathrm{Cu}}^{65}$ with a cross section of a few millibarns.