Energy levels ofCf250populated in theβ−decay ofBk250

The level scheme of doubly even ${}_{98}{}^{250}{}_{}{}^{}\mathrm{Cf}_{152}^{}{}_{}{}^{}$ has been studied from the ${\beta }^{-}$ decay of ${}_{}{}^{250}{}_{}{}^{}\mathrm{Bk}$. $\gamma$-ray energy and intensity measurements were made using Ge(Li) and Si(Li) detectors. Analysis of $\gamma$-singles and $\gamma -\gamma$ coincidence data has revealed the existence of ∼ 46 $\gamma$-ray transitions. Approximately 40 of these, accounting for ≳ 99.97% of the observed $\gamma$-ray intensity, have been incorporated into a level scheme for ${}_{}{}^{250}{}_{}{}^{}\mathrm{Cf}$ consisting of 17 excited states with excitation energies up to 1695 keV. The following states, whose $I^{\pi }$ values and energies (in keV) are well known from other experiments, are observed: the $0^{+}$(0), $2^{+}$(42.73), and $4^{+}$(141.89) members of the ground-state band; the $2^{-}$(871.56), $3^{-}$(905.85), and $4^{-}$(952.0) members of the $K^{\pi }=2^{-}$ octupole band; and the $2^{+}$(1031.85) and $3^{+}$(1071.38) members of the $\gamma$-vibrational band. In addition, evidence is presented which permits the following $I$, $K^{\pi }$ assignments to be made with reasonable confidence (the corresponding level energies—in keV—are given in parentheses): 1,$1^{-}$(1175.5); 2,$2^{+}$(1244.50); 2,$0^{+}$(1296.64); 2,$2^{+}$(1657.99); and 3,$2^{+}$(1695.2). The half-life of ${}_{}{}^{250}{}_{}{}^{}\mathrm{Bk}$ has been remeasured and a value of 192.7±0.3 m obtained. The absolute intensities (in photons/100 ${}_{}{}^{250}{}_{}{}^{}\mathrm{Bk}$ has been remeasured and a value of 192.7±0.3 m obtained. The absolute intensities (in photons/100 ${}_{}{}^{250}{}_{}{}^{}\mathrm{Bk}$ ${\beta }^{-}$ decays) of the prominent 989- and (1028±1031)-keV $\gamma$ rays have been measured using a $4\pi \beta -\gamma$ coincidence system and values of 45.0±0.8 and 40.6±0.7, respectively, have been obtained.