Levels ofCs138Fed in theβ-Decay ofXe138

The energy levels of ${}_{}{}^{138}{}_{}{}^{}\mathrm{Cs}$ populated in the decay of 14.2-min ${}_{}{}^{138}{}_{}{}^{}\mathrm{Xe}$ have been investigated using on-line techniques. The $\gamma$-ray energies and intensities in the range 0.1-2.5 MeV were determined with Ge(Li) detectors. Using a Si(Li) x-ray detector, a 10.7-keV $\gamma$ ray was found and its $L$-shell conversion coefficient determined to be 150 ± 70. Conversion-electron lines have been measured with a Si(Li) detector and the following $K$ conversion coefficients have been calculated (transition energies in keV, within brackets): (290 ± 30) × ${10}^{-3\mathrm{}}$ [154.0], (62 ± 14) × ${10}^{-3\mathrm{}}$ [242.8], (56 ± 5) × ${10}^{-3\mathrm{}}$ [258.5], (16 ± 3) × ${10}^{-3\mathrm{}}$ [396.7], (37 ± 8) × ${10}^{-3\mathrm{}}$ [401.5], and (15 ± 2) × ${10}^{-3\mathrm{}}$ [434.6]. Ge(Li)-Ge(Li) and Si(Li)-Ge(Li) $\gamma -\gamma$ coincidences have been measured. From these experiments the following level sequence is proposed (energies in keV, $J^{\pi }$ within brackets): 0 [$3^{\mathrm{}(-)\mathrm{}}$]; 10.79 ± 0.11 [$2^{\mathrm{}(-)\mathrm{}}$]; 15.71 ± 0.12 [$1^{\mathrm{}(-)\mathrm{}}$, $0^{\mathrm{}(-)\mathrm{}}$, $2^{\mathrm{}(-)\mathrm{}}$]; 258.49 ± 0.11 [$2^{\mathrm{}(-)\mathrm{}}$, $1^{\mathrm{}(-)\mathrm{}}$]; 412.45 ± 0.16 [$1^{\mathrm{}(-)\mathrm{}}$]; 450.33 ± 0.16 [$0^{\mathrm{}(-)\mathrm{}}$, $1^{\mathrm{}(-)\mathrm{}}$]; 541.05 ± 0.13; 815.7 ± 0.4; 876.21 ± 0.22; 912.62 ± 0.14 [$1^{\mathrm{}(-)\mathrm{}}$, $2^{\mathrm{}(-)\mathrm{}}$]; 951.6 ± 0.4; 1109.67 ± 0.17; 1127.0 ± 0.3 [$0^{\pm }$, $1^{\pm }$, $2^{-}$]; 1367.5 ± 0.3; 1395.8 ± 0.4; 1489.0 ± 0.4; 2026.67 ± 0.17 [$1^{+}$]; 2263.01 ± 0.23 [$1^{+}$]; 2337.62 ± 0.19 [$1^{+}$]; 2468.5 ± 0.5 [0, 1]; and 2509.00 ± 0.24 [$1^{+}$].