The nuclides ${}_{}{}^{43}{}_{}{}^{}\mathrm{Ar}$ and ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ar}$ have been produced by spallation reactions on vanadium targets at $E_p=600\mathrm{}$ MeV. The subsequent $\beta$ decays to ${}_{}{}^{43}{}_{}{}^{}\mathrm{K}$ and ${}_{}{}^{44}{}_{}{}^{}\mathrm{K}$ have been studied via delayed $\gamma$-ray singles and $\gamma -\gamma$ coincidence techniques. In ${}_{}{}^{43}{}_{}{}^{}\mathrm{K}$, excitation energies and $\gamma$-branching fractions have been determined for 19 levels. The $log\mathrm{ft}$ values imply $J^{\pi }=\frac{3}{2^{-}}, \frac{5}{2^{\pm }}$ for the ground state of ${}_{}{}^{43}{}_{}{}^{}\mathrm{Ar}$. For ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ar}$, evidence is found for four new $\beta$ branches and $J^{\pi }=1^{+}$ is assigned to the levels at 2326 and 2574 keV on the basis of the $\beta$ decay selection rules. The proposed decay scheme accounts for $\gamma$ transitions between 10 levels, the first excited state being located at 182.6 keV. The structure of these nuclei is discussed in the weak coupling scheme.

RADIOACTIVITY ${}_{}{}^{43,44}{}_{}{}^{}\mathrm{Ar}$ from ${}_{}{}^{50,51}{}_{}{}^{}\mathrm{V}(p, 6pxn)$, natural target, mass separated measured delayed $E_{\gamma }$, $I_{\gamma }$, $\gamma -\gamma$ coincidences, deduced decay schemes, $log\mathrm{ft}$, $J$, $\pi$.

• Received 8 June 1978

DOI:https://doi.org/10.1103/PhysRevC.18.1803