Positron-gamma coincidence measurements have been carried out on ${\mathrm{N}}^{12}$ by forming the activity in the ${\mathrm{B}}^{10}({\mathrm{He}}^3,n){\mathrm{N}}^{12}$ reaction using a mechanically chopped Van de Graaff beam of 3.4-MeV ${\mathrm{He}}^{3+}$ ions and by detecting the delayed positron and gamma radiations in plastic and NaI(Tl) scintillation detectors. Gamma rays with energies of 4.43, 12.7, and 15.1 MeV were observed in coincidence with positrons. For the two higher states, the ${\mathrm{N}}^{12}$ positron branches and $log\mathrm{ft}$ values derived are (2.9±1.3)×${10}^{-3\mathrm{}}$, $logft=3.55\mathrm{}\pm 0.16$ for positron emission to the 12.71-MeV state of ${\mathrm{C}}^{12}$, and (4.4±1.5)×${10}^{-5\mathrm{}}$, $logft=3.32\mathrm{}\pm 0.13$ for the positron transition to the 15.11-MeV state of ${\mathrm{C}}^{12}$.

• Received 17 August 1966

DOI:https://doi.org/10.1103/PhysRev.153.1061