Medium-spin states of ${}^{70}\mathrm{Ge}$ have been studied via the ${}^{60}\mathrm{Ni}$(${}^{12}\mathrm{C}$,2$p\gamma$)${}^{70}\mathrm{Ge}$ reaction at 45 MeV. The ground-state band and the second $0^{+}$ band have been extended to the ${12}^{+}$ and $8^{+}$ states, respectively. Two negative-parity bands, one of which has a coupled structure and the other has a decoupled structure, have been observed additionally. Although the latter decoupled structure was known up to the (${21}^{-}$) state from a previous experiment, the part of the level scheme up to the ${15}^{-}$ state has been largely modified by the present experiment. Backbendings observed in the positive- and negative-parity yrast bands have been compared with those of the neighboring even Ge isotopes. The experimental level structure has been compared with the shell-model calculations in the model space ($2p_{3/2}$, $1f_{5/2}$, $2p_{1/2}$, $1g_{9/2}$) employing two kinds of effective interactions, one of which is an extended $P+\mathit{QQ}$ interaction with monopole interactions and the other is developed from a renormalized $G$ matrix. Microscopic structures of the observed bands have been discussed with the help of the shell-model calculations.

• Received 6 October 2009

DOI:https://doi.org/10.1103/PhysRevC.81.024309