Signature-dependenct proton alignments at high rotational frequency and the persistence of proton pairing correlations.

Abstract

Band crossings are observed in the yrast $\ensuremath{\alpha}=\ensuremath{-}\frac{1}{2} \mathrm{and} +\frac{1}{2}$ negative-parity decay sequences in $^{157}\mathrm{Ho}$ at $\ensuremath{\hbar}\ensuremath{\omega}=0.48 \mathrm{and} \ensuremath{\approx}0.54$ MeV, respectively. These band crossings are interpreted as the alignment of the second and probably the third pair of ${h}_{\frac{11}{2}}$ quasiprotons. This is the first identification of delayed crossings involving the second aligning nucleon. These crossings show that sizable proton-pair correlations must remain for these configurations up to high rotational frequencies $\ensuremath{\hbar}\ensuremath{\omega}\ensuremath{\approx}0.5$ MeV.