The spectrum shape for the 4.12-MeV ${\mathrm{O}}^{14}$ → ${\mathrm{N}}^{14}$ allowed positron transition has been measured in the positron energy range greater than 2 MeV. The observed shape deviates markedly from the statistical shape (slope about - 11% per MeV at 3 MeV). The $\int \alpha \times \mathrm{r}$ forbidden matrix element is extracted from the data and used to calculate the mean life of ${\mathrm{N}}^{14*}$. For the latter, the value obtained is (3.3±0.3) × ${10}^{-14\mathrm{}}$ sec. The sign of the allowed matrix element $\int \sigma$ is found to be positive. The $\mathrm{ft}$ value obtained for the 4.12-MeV transition is (2.14±0.03) × ${10}^7$ sec and the branching fraction is found to be (0.61±0.01)%.

• Received 28 March 1966

DOI:https://doi.org/10.1103/PhysRev.148.1024