The $\gamma$ radiation following the decay of ${}_{}{}^{144}{}_{}{}^{}\mathrm{Ba}$ to ${}_{}{}^{144}{}_{}{}^{}\mathrm{La}$ was measured with a variety of detectors in experiments where $\gamma$-ray singles, time dependent $\gamma$-ray spectra, $\gamma \gamma t$ coincidence, and $\gamma \gamma t$ angular correlation data were collected. The ${}_{}{}^{144}{}_{}{}^{}\mathrm{Ba}$ activity was produced by on-line mass separation from the products of the ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}(n, f)$ reaction. The half-life of ${}_{}{}^{144}{}_{}{}^{}\mathrm{Ba}$ was determined to be 11.5±0.2 s. A level scheme for odd-odd ${}_{}{}^{144}{}_{}{}^{}\mathrm{La}$ was deduced from coincidence information in which 91 $\gamma$ rays were placed among 26 levels. Internal conversion and angular correlation measurements yielded spin-parity assignments for several levels. Several features of the level scheme are discussed including the $\beta$ decay to low-lying levels and the possible core-coupled structure of the $1^{+}$ levels.

RADIOACTIVITY ${}_{}{}^{144}{}_{}{}^{}\mathrm{Ba}$ [from ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}(n_{\mathrm{th}}, f)$], measured $t_{\frac{1}{2}}$, $E_{\gamma }$, $I_{\gamma }$, ${\alpha }_K$, $\gamma \gamma$ coincidence, $\gamma \gamma \left(\theta \right)$ angular correlation; HPGe, Ge(Li), and LEPS detectors; ${}_{}{}^{144}{}_{}{}^{}\mathrm{La}$ deduced levels, $J^{\pi }$, $I_{\beta }$, $\delta$, and $log\mathrm{ft}$. Mass-separated ${}_{}{}^{144}{}_{}{}^{}\mathrm{Ba}$ activity.

• Received 10 March 1982

DOI:https://doi.org/10.1103/PhysRevC.26.1198