Three odd-odd $N=73\mathrm{}$ isotones, namely ${}^{128}\mathrm{Cs},$ ${}^{130}\mathrm{La},$ and ${}^{132}\mathrm{Pr},$ have been studied via (HI, $\mathrm{xn}\gamma )$ reactions. In all three cases, $\Delta I=1\mathrm{}$ side bands of the $\pi h_{11/2}\nu h_{11/2}$ yrast bands were discovered. This extends the systematic observation of nearly degenerate $\pi h_{11/2}\nu h_{11/2}$ doublet bands in the neighboring $N=75\mathrm{}$ isotones; these were interpreted as resulting from chiral symmetry breaking in the intrinsic body-fixed frame.

• Received 17 January 2001

DOI:https://doi.org/10.1103/PhysRevC.63.061304