Mass ofGe64and Its Role in Nucleosynthesis

The mass of the $N=Z$ nucleus ${}_{32}{}^{64}{}_{}{}^{}\mathrm{Ge}$ has been measured by determining the positron endpoint energy from the prominent decay to the 427-keV state in ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ga}$. The ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}({}_{}{}^{12}{}_{}{}^{}\mathrm{C},2n){}_{}{}^{64}{}_{}{}^{}\mathrm{Ge}$ reaction was used to produce ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ge}$, at a bombarding energy of 36 MeV. Off-line ${\beta }^{+}-\gamma$ coincidences were studied, as well as the half-life of the 427-keV transition. The half-life was observed to be 70 ± 7 sec, in agreement with a previous measurement. The observed endpoint energy was 2.96 ± 0.25 MeV, leading to a total decay energy of 4.41 ± 0.25 MeV, and a mass excess of -54.43 ± 0.25 MeV for ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ge}$. Implications for nucleosynthesis and the solar system abundance of ${}_{}{}^{64}{}_{}{}^{}\mathrm{Zn}$ are discussed.