New $\beta$-decaying state in $^{214}$Bi

A new $\beta$-decaying state in $^{214}$Bi has been identified at the ISOLDE Decay Station at the CERN-ISOLDE facility. A preferred $I^{\pi} = (8^-)$ assignment was suggested for this state based on the β-decay feeding pattern to levels in $^{214}$Po and shell-model calculations. The half-life of the $I^{\pi} = (8^-)$ state was deduced to be $T_{1/2} = 9.39(10)$ min. The deexcitation of the levels populated in $^{214}$Po by the $\beta$ decay of this state was investigated via $\gamma - \gamma$ coincidences and a number of new levels and transitions was identified. Shell-model calculations for excited states in $^{214}$Bi and $^{214}$Po were performed using two different effective interactions: the H208 and the modified Kuo-Herling particle interaction. Both calculations agree on the interpretation of the new β-decaying state as an $I^{\pi} = 8^-$ isomer and allow for tentative assignment of shell-model states to several high-spin states in $^{214}$Po.