Beta Decays ofC15,F17, andF20

Abstract

$\beta$-ray branches in the decays of ${\mathrm{C}}^{15}$, ${\mathrm{F}}^{17}$, and ${\mathrm{F}}^{20}$ have been investigated by measuring the $\gamma$-ray spectra from these activities with a 22-cc Ge(Li) detector. The activities were formed by deuteron bombardment of various targets with a chopped Van de Graaff beam. Previously observed ${\mathrm{C}}^{15}$ $\beta$-ray branches to the 8312-and 9052-keV states of ${\mathrm{N}}^{15}$ were confirmed, the branches being [(5.0±0.6)×${10}^{-4\mathrm{}}$; $logft=5.06\mathrm{}\pm 0.06$] and [(3.5±0.5)×${10}^{-4\mathrm{}}$; $logft=3.99\mathrm{}\pm 0.07$], respectively, and one new branch was found leading to the 7300-keV state [(0.8±0.2)×${10}^{-4\mathrm{}}$; $logft=6.82\mathrm{}\pm 0.13$]. There is also weak evidence for a $\beta$-ray branch to the 8570-keV state of ${\mathrm{N}}^{15}$[≤2.8×${10}^{-4\mathrm{}}$; $log\mathrm{ft}\ge 5.0$]. The limit on the $\beta$ branching of ${\mathrm{F}}^{17}$ to the 871-keV state of ${\mathrm{O}}^{17}$ is ${10}^{-4\mathrm{}}$, corresponding to $log\mathrm{ft}>\mathrm{}5.6\mathrm{}$. In ${\mathrm{F}}^{20}$ decay, lifetime measurements have confirmed that a weak 3.3-MeV $\gamma$ ray is associated with this activity resulting from a $\beta$-ray branch to the 4.97-MeV state of ${\mathrm{Ne}}^{20}$[(1.7±0.3)×${10}^{-4\mathrm{}}$; $logft=6.89\mathrm{}\pm 0.08$]. From simultaneous measurements on the $\gamma$ rays occurring in ${\mathrm{F}}^{20}$ and ${\mathrm{B}}^{12}$ decays, the energy of the ${\mathrm{F}}^{20}$ $\gamma$ ray is 3334.3±0.7 keV, and thus ${\mathrm{Ne}}^{20}$ level has an energy of 4968.3±0.8 keV.