Absolute Cross Section of the Reaction Cu63(γ, n)Cu62 for Lithium Gamma Rays

The cross section of the reaction Cu 63 (γ, n )Cu 62 for Li gamma rays was measured in order to discover some causes of the existing discrepancy between values measured by bremsstrahlungs and by nuclear gamma rays. Experimental procedures used in this experiment were much improved as compared with those used in previous measurements performed in our laboratory for the same purpose. The present results were as follows: \begin{aligned} \sigma_{\text{Li-$\gamma$}}{=}62{\pm}4\ \text{mb for Li gamma rays}, \end{aligned} and \begin{aligned} \sigma_{17.6}{=}76{\pm}5\ \text{mb for} 17.6 \text{Mev $\gamma$-rays}. \end{aligned} This value is about 30 per cent lower than the average cross section value determined by the photon difference method in several bremsstrahlungs' experiments. Therefore, we suggest that the modified spectrum method proposed by Penfold and Leiss might eliminate not only the above-mentioned discrepancy but also the discrepancy between theoretical and experimental values in the form \(\sigma_{-...