Beta-Ray Spectrum ofN16

The beta-ray spectrum of 7.38-second ${\mathrm{N}}^{16}$ has been investigated with a 180-degree magnetic spectrometer. The radioactive nuclei were produced by 1.5-Mev deuterons through the reaction ${\mathrm{N}}^{15}(d, p){\mathrm{N}}^{16}$, using targets of lead nitrate enriched to 64% in ${\mathrm{N}}^{15}$. Of the four known beta-ray groups, two with end-point energies 10.40±0.05 Mev and 4.39±0.07 Mev are satisfactorily resolved. The intensity of the 10.40-Mev group relative to that of the remainder of the transitions is in the ratio of 28:72, leading to $log{f}_{0}t=6.67\mathrm{}$. The 10.40-Mev group is shown to proceed as a first-forbidden $\Delta J=2\left(\mathrm{yes}\right)$ transition, and thus the ground state of ${\mathrm{N}}^{16}$ may be uniquely designated as a $2^{-}$ level.