This is the first report on nuclear structure of ${}_{}{}^{109}{}_{}{}^{}\mathrm{Sb}$. Excited states up to ${\mathit{I}}^{\mathrm{\pi }}$=27/$2^{+}$ and 35/$2^{\mathrm{-}}$ have been established using the reaction ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$${(}^{58}$Ni, 3p${)}^{109}$Sb and in-beam techniques. According to the particle(hole)-core coupling scheme these excited states were classified into five bands: three are based on the π${\mathit{d}}_{5/2}$, π${\mathit{g}}_{7/2}$, and π${\mathit{h}}_{11/2}$ states; the other two are the ΔI=1 collective bands built on the 17/$2^{+}$ state at 2651 keV and the 23/$2^{\mathrm{-}}$ state at 4487 keV. The 11/$2^{+}$→9/$2^{+}$ transition in the π${\mathit{g}}_{7/2}$ band possesses an E2/M1 mixing ratio δ>0, which suggests admixing of the π${\mathit{g}}_{9/2}$ hole state. Positive mixing ratios observed in the collective bands indicate a prolate deformation due to the (π${\mathit{g}}_{9/2}$${)}^{\mathrm{-}1}$ core excitation. In the π${\mathit{h}}_{11/2}$ band, B(M1;23/$2^{\mathrm{-}}$→21/$2^{\mathrm{-}}$) was measured to be 0.040(3) W.u. Furthermore the 27/$2^{\mathrm{-}}$→25/$2^{\mathrm{-}}$ transition was too weak for a proton M1 transition. These transitions are retarded by the ν${\mathit{h}}_{11/2}$ configurations mixed in the involved states.

• Received 6 December 1993

DOI:https://doi.org/10.1103/PhysRevC.49.2982