Structure studies of 257Db through combined α, γ and internal-conversion-electron spectroscopy

Abstract

This work reports on the study of the decay properties along the ${}^{257}$Db decay chain using the GABRIELA setup. The first observation of a high-K isomer in ${}^{257}$Db is presented. In addition, an unreported $\hat{I}\pm$-decay branch in ${}^{249}$Md has been evidenced, allowing to constrain the differences in energy of the $\hat{I}\pm$-decaying levels in ${}^{249}$Md, ${}^{253}$Lr and ${}^{257}$Db. Finally, the combination of the observed fine structure $\hat{I}\pm$-decay from the high-spin state in ${}^{257}$Db with the first observation the internal decay in ${}^{253}$Lr requires a revision of level and decay scheme. In particular, a change of parity for the high-spin state from 9/2${}^{+}$ to 9/2${}^{-}$ in the ${}^{257}$Db is suggested, and the implications of such a change are also discussed.

accepted for publication in PRC in June 2025