The decay of ${}_{56}{}^{148}{}_{}{}^{}\mathrm{Ba}_{92}^{}{}_{}{}^{}$ to levels of odd-odd ${}_{57}{}^{148}{}_{}{}^{}\mathrm{La}_{91}^{}{}_{}{}^{}$ has been studied in experiments where $\gamma$-ray singles, time-dependent $\gamma$-ray spectra, and $\gamma \gamma t$ coincidence spectra were collected. The ${}_{}{}^{148}{}_{}{}^{}\mathrm{Ba}$ activity was produced directly by on-line mass separation. The half-life of ${}_{}{}^{148}{}_{}{}^{}\mathrm{Ba}$ was determined to be 0.61±0.03 s. A level scheme containing 26 levels and 63 $\gamma$ rays is proposed for ${}_{}{}^{148}{}_{}{}^{}\mathrm{La}$. Spin and parity for several low-lying levels are assigned on the basis of internal conversion coefficient measurements and $\beta$- and $\gamma$-ray branching. A half-life of 67±4 ns is measured for the 56-keV level. Several features of the level scheme are discussed and compared to neighboring La isotopes and $N=91\mathrm{}$ isotones.

[RADIOACTIVITY ${}_{}{}^{148}{}_{}{}^{}\mathrm{Ba}$ [from ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}({\mathrm{n}}_{\mathrm{th}},f)$] measured $E_{\gamma },I_{\gamma },{\alpha }_k,t_{\frac{1}{2}},\gamma \gamma t$ coincidence, LEPS and HpGe detectors; ${}_{}{}^{148}{}_{}{}^{}\mathrm{La}$ deduced levels, $I_{\beta },J^{\pi }$, and level halflife. Mass separated ${}_{}{}^{148}{}_{}{}^{}\mathrm{Ba}$ activity.]

• Received 10 June 1983

DOI:https://doi.org/10.1103/PhysRevC.29.592