In a series of ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ti}$ bombardments of ${}_{}{}^{144}{}_{}{}^{}\mathrm{Sm}$ the decay energy of the ${}_{}{}^{189}{}_{}{}^{}\mathrm{Bi}_{}^{\mathit{m}}{}_{}{}^{}$ (π${\mathit{s}}_{1/2}$) α transition that proceeds to the (π${\mathit{s}}_{1/2}$) ground state of ${}_{}{}^{185}{}_{}{}^{}\mathrm{Tl}$ was measured to be 7.30(4) MeV. This result establishes the excitation energy of ${}_{}{}^{189}{}_{}{}^{}\mathrm{Bi}_{}^{\mathit{m}}{}_{}{}^{}$ as 190(40) keV rather than the adopted 92(10)-keV value. Our data indicate a leveling off in excitation energy at N≊106 for the ${\mathit{s}}_{1/2}$ intruder state in the odd-A Bi isotopes rather than a continued drop at that neutron number as inferred by Coenen et al. in their discussion of intruder state systematics in the Pb region. Consequences of this discrepancy for the adopted excitation energy of the π${\mathit{s}}_{1/2}$ isomer in ${}_{}{}^{187}{}_{}{}^{}\mathrm{Bi}$ are discussed.

• Received 19 June 1995

DOI:https://doi.org/10.1103/PhysRevC.52.1807