Shell-model description for the properties of the forbidden ${\beta }^{-}$ decay in the region "north-east" of ${}^{208}$Pb

In the present work, we report a comprehensive shell-model study of the $\log ft$ values for the forbidden ${\beta }^{-}$ decay transitions in the north-east region of ${}^{208}$Pb. For this we have considered ${}^{210-215}$Pb $\to$ ${}^{210-215}$Bi and ${}^{210-215}$Bi $\to$ ${}^{210-215}$Po transitions. We have performed shell-model calculation using KHPE interaction in valence shell 82-126 for protons and 126-184 for neutrons without any truncation. We have also calculated half-lives and Q-values for the concerned nuclei. Recently several $\log ft$ values are observed corresponding to ${\beta }^{-}$ decay from (8${}^{-}$) isomeric state of ${}^{214}$Bi${}^m$ at CERN-ISOLDE facility [Phys. Rev. C {\bf 104}, 054301 (2021)], and for the first time we have reported shell-model results for these transitions.