Beta Decay ofCl39

The ${\beta }^{-}$ decay of ${\mathrm{Cl}}^{39}$ to states of ${\mathrm{Ar}}^{39}$ has been studied using a Ge(Li) detector. ${\mathrm{Cl}}^{39}$ was produced in the reaction ${\mathrm{Cl}}^{37}\mathrm{}(t,p)\mathrm{}{\mathrm{Cl}}^{39}$ at $E_t=3.0\mathrm{}$ MeV by bombarding Ba${\mathrm{Cl}}_2$ targets enriched to 96.1% in ${\mathrm{Cl}}^{37}$. The half-life was measured to be 56.2 ± 0.6 min. Ten $\gamma$-ray transitions were observed including seven $\gamma$ rays not seen previously in the ${\mathrm{Cl}}^{39}$ decay. Ge(Li) versus NaI(Tl) coincidence measurements were used to determine the placement of these $\gamma$-ray transitions in the ${\mathrm{Ar}}^{39}$ level scheme. The measured $\gamma$-ray intensities determine new $\beta$-ray branches of ≤0.08%, (2.61 ± 0.11)%, (2.29 ± 0.12)%, and (0.60 ± 0.05)% to ${\mathrm{Ar}}^{39}$ levels at 2093, 2358, 2503, and 2829 keV with $\mathrm{lof}\mathrm{ft}$ values of ≥8.03, 6.14 ± 0.04, 5.96 ± 0.04, and 5.84 ± 0.06, respectively. The latter two $log\mathrm{ft}$ values lead to spin restrictions of $\frac{1}{2}$, $\frac{3}{2}$, or $\frac{5}{2}$ for the 2305- and 2829-keV ${\mathrm{Ar}}^{39}$ levels and strongly suggest even parity for both states. Other previously observed $\beta$-ray branches have been confirmed. Accurate excitation energies with errors between 0.05 and 1.0 keV have been obtained for the ${\mathrm{Ar}}^{39}$ states involved.