High-spin states of ${}^{138}\mathrm{Pm}$ have been populated using the ${}^{124}\mathrm{Te}({}^{19}\mathrm{F},5\mathrm{n}){}^{138}\mathrm{Pm}$ reaction at a beam energy of 105 MeV. A new positive-parity side band with the same $\pi h_{11/2}\otimes \nu h_{11/2}$ configuration as that of the yrast band is observed in ${}^{138}\mathrm{Pm}$. The properties of the two positive-parity bands show general agreement with the fingerprints of chiral rotation and thus these two bands are suggested to be candidates for near degenerate chiral doublet bands. Besides, odd-even spin staggering of the $\pi h_{11/2}\otimes \nu h_{11/2}$ bands is studied systematically in odd-odd Cs, La, Pr, and Pm isotopes. As a result of this study we suggest that the spin value of lowest observed state of the yrast band be reassigned as 9 in ${}^{138}\mathrm{Pm}$. This new spin assignment is also supported by the argument of alignment additivity.

• Received 18 October 2017

DOI:https://doi.org/10.1103/PhysRevC.97.014305