Threshold for the Proton-Neutron Reaction in Copper

Abstract

The direct determination of the ($p,n$) threshold for ${\mathrm{Cu}}^{65}$ has been found. The energy of the ${\mathrm{Li}}^{7}(p,n)$ threshold had been previously checked against the $\mathrm{F}(p,\ensuremath{\gamma})$ resonances, and the value, 1.85\ifmmode\pm\else\textpm\fi{}0.01 Mev of this threshold of ${\mathrm{Li}}^{7}$ was used as the voltage standard in this experiment. The value for the ${\mathrm{Cu}}^{65}(p,n)$ threshold was found to be 2.164\ifmmode\pm\else\textpm\fi{}0.01 Mev. If the mass of ${\mathrm{Cu}}^{65}$ is taken as 64.955, the mass for ${\mathrm{Zn}}^{65}$ is computed to be 64.9565\ifmmode\pm\else\textpm\fi{}0.001. If after positron emission the resultant nucleus is in the ground state, the maximum energy of the positron spectrum may be computed to be 0.355\ifmmode\pm\else\textpm\fi{}0.001.