Frequency and Alignment Classification of Multiple Band Crossings

Abstract

Experiments on ${}_{}{}^{160}{}_{}{}^{}\mathrm{Yb}$ indicate three negative-parity bands up to $I>~21\hslash$. All three experience a band crossing around a frequency $\hslash \omega =0.36\mathrm{}$ MeV, a value intermediate to those of the first and second yrast backbends. The $i_{\frac{13}{2}}$ band in ${}_{}{}^{161}{}_{}{}^{}\mathrm{Yb}$ is observed up to ${\frac{49}{2}}^{+}$; it also has a strong upbend at this intermediate frequency. The fingerprint of a band crossing based upon the crossing frequency and gain in aligned angular momentum is demonstrated and the results compared to cranking-model calculations to suggest quasiparticle assignments for the bands.