The ${\mathrm{C}}^{12}({\mathrm{He}}^3, p\gamma ){\mathrm{N}}^{14}$ reaction has been used to study the electromagnetic decay of the 3.95- and 7.03-MeV states of ${\mathrm{N}}^{14}$. Angular distributions of the 3.95 → 0 and 3.95 → 2.31 transitions were measured with a three-crystal pair spectrometer at a ${\mathrm{He}}^3$ bombarding energy of 2.2 MeV. Analyses of these data determine solutions for $x$, the $\frac{E2\mathrm{}}{M1\mathrm{}}$ mixing ratio for the ground-state transition, of $x=-(0.37\mathrm{}\pm 0.04)$ or $x=-(2.80\mathrm{}\pm 0.27)$, where the phase convention is that of Litherland and Ferguson. Branching ratios of (3.7±0.3)% and (96.3±0.3)% were determined for transitions from the 3.95-MeV state to the ground state and to the 2.31-MeV first excited state, respectively. Combining these results with the previously determined $E2\mathrm{}$ radiative width of the 3.95 → 0 transition, it is seen that the smaller (in magnitude) solution for $x$ corresponds to an inordinately large $M1\mathrm{}$ strength for both the 3.95 → 0 $\Delta T=0\mathrm{}$ and 3.95 → 2.31 $\Delta T=1\mathrm{}$ transitions. For the larger value, $x=-(2.80\mathrm{}\pm 0.27)$, the radiative widths are ${\Gamma }_{\gamma }\mathrm{}\left(M1\mathrm{}\right)=0.140\mathrm{}\pm 0.013$ eV for the 3.95 → 2.31 transition and ${\Gamma }_{\gamma }\mathrm{}\left(M1\mathrm{}\right)=(5.8\mathrm{}\pm 1.2)\times {10}^{-4\mathrm{}}$ eV for the 3.95 → 0 transition. Gamma-ray coincidence studies employing NaI(Tl) spectroscopy were also carried out at a ${\mathrm{He}}^3$ bombarding energy of 6.0 MeV to determine the gamma branching of the ${\mathrm{N}}^{14}$ 7.03-MeV level to known lower lying levels. Branchings of (0.5±0.1)% and (0.9±0.25)% were determined for transitions to the first and second excited states of ${\mathrm{N}}^{14}$, respectively, while upper limits of 0.4% (or less) were placed on possible transitions to the other excited states. Combining this with previous work gives an $E2\mathrm{}$ radiative width for the 7.03 → 2.31 $\Delta T=1\mathrm{}$ transition of (6±1.4)×${10}^{-4\mathrm{}}$ eV, and a total radiative width for the 7.03 → 3.95 $\Delta T=0\mathrm{}$ transition of (11±3)×${10}^{-4\mathrm{}}$ eV.

• Received 27 September 1966

DOI:https://doi.org/10.1103/PhysRev.154.971