Signature-Dependent Proton Alignments at High Rotational Frequency and the Persistence of Proton Pairing Correlations

Band crossings are observed in the yrast $\alpha =-\frac{1}{2} \mathrm{and} +\frac{1}{2}$ negative-parity decay sequences in ${}_{}{}^{157}{}_{}{}^{}\mathrm{Ho}$ at $\hslash \omega =0.48\mathrm{} \mathrm{and} \approx 0.54$ 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 $\hslash \omega \approx 0.5$ MeV.