Beta Decay of Cl39

The β^- decay of Cl³⁹ to states of Ar³⁹ has been studied using a Ge(Li) detector. Cl³⁹ was produced in the reaction Cl³⁷(t,p)Cl³⁹ at E_t=3.0 MeV by bombarding BaCl₂ targets enriched to 96.1% in Cl³⁷. The half-life was measured to be 56.2 +/- 0.6 min. Ten γ-ray transitions were observed including seven γ rays not seen previously in the Cl³⁹ decay. Ge(Li) versus NaI(Tl) coincidence measurements were used to determine the placement of these γ-ray transitions in the Ar³⁹ level scheme. The measured γ-ray intensities determine new β-ray branches of <=0.08%, (2.61 +/- 0.11)%, (2.29 +/- 0.12)%, and (0.60 +/- 0.05)% to Ar³⁹ levels at 2093, 2358, 2503, and 2829 keV with lofft values of >=8.03, 6.14 +/- 0.04, 5.96 +/- 0.04, and 5.84 +/- 0.06, respectively. The latter two ft values lead to spin restrictions of 12, 32, or 52 for the 2305- and 2829-keV Ar³⁹ levels and strongly suggest even parity for both states. Other previously observed β-ray branches have been confirmed. Accurate excitation energies with errors between 0.05 and 1.0 keV have been obtained for the Ar³⁹ states involved.