Intruder rotational bands have been investigated to high frequency in ${}_{51}{}^{109}{}_{}{}^{}\mathrm{Sb}$. Five decoupled (ΔI=2) bands extending to rotational frequencies above 1.4 MeV/ħ have been observed. At the highest frequencies, the ${\mathit{J}}^{\mathrm{}\left(2\right)\mathrm{}}$ dynamic moments of inertia for four of these bands are seen to decrease steadily to unexpectedly low values, ${\mathit{J}}^{\mathrm{}\left(2\right)\mathrm{}}$ ∼ 10 ${\mathrm{ħ}}^2$ ${\mathrm{MeV}}^{\mathrm{-}1}$. These four bands, which are interpreted as being based on deformed 2p-2h proton excitations across the Z=50 closed-shell gap, achieve the so-called ‘‘smooth band termination’’ following alignment of the valence nucleons outside of ${}_{}{}^{100}{}_{}{}^{}\mathrm{Sn}$. In addition, two strongly coupled (ΔI=1) bands have been observed, which are related to 1p-1h proton excitations across the gap. © 1996 The American Physical Society.

• Received 8 February 1996

DOI:https://doi.org/10.1103/PhysRevC.54.1598