A new activity, ${\mathrm{O}}^{14}$, has been produced from ${\mathrm{N}}^{14}$ by a ($\mathrm{pn}$) reaction and is found to decay with a half-life of 76.5±2 sec. by the emission of 1.8±0.1-Mev positrons and a 2.3-Mev gamma-ray. Rough threshold measurements indicate that the gamma- and beta-rays are in cascade. ${\mathrm{C}}^{10}$, formed by a ($\mathrm{pn}$) reaction in ${\mathrm{B}}^{10}$, has been carefully reexamined and shown to decay with a half-life of 19.1±0.8 sec. by the emission of 2.2±0.1-Mev positrons and a gamma-ray of approximately 1 Mev. The Coulomb energy formula for this type of mirror nucleus is shown to be valid, but the same theoretical difficulties are encountered here as are already known from the long lives of ${\mathrm{Be}}^{10}$ and ${\mathrm{C}}^{14}$.

• Received 4 October 1948

DOI:https://doi.org/10.1103/PhysRev.75.282