Collective bands based on a low-K π$h_{11/2}$ orbital have been populated to high spins in the odd-proton nuclei ${}_{}{}^{135}{}_{}{}^{}$,137Pm following the reactions ${}_{}{}^{116}{}_{}{}^{}\mathrm{Sn}$${(}^{24}$Mg,p4n${)}^{135}$Pm and ${}_{}{}^{114}{}_{}{}^{}\mathrm{Cd}$${(}^{27}$Al,4n${)}^{137}$Pm, respectively. Both nuclei exhibit a band crossing in the π$h_{11/2}$ band at a frequency of ħω∼0.42 MeV. In ${}_{}{}^{135}{}_{}{}^{}\mathrm{Pm}$, an upbend is observed, while a weaker interaction backbend is observed in ${}_{}{}^{137}{}_{}{}^{}\mathrm{Pm}$. Cranked-shell model calculations, including triaxiality, imply that this crossing is due to the alignment of the second and third valence $h_{11/2}$ protons. The systematics of this alignment in the Pm isotopes will be discussed. In addition, positive parity three-quasiproton states were observed in both nuclei. These structures also contain a pair of aligned $h_{11/2}$ protons, in this case the first and second valence protons which align at a much lower frequency of ħω∼0.28 MeV.

• Received 21 April 1987

DOI:https://doi.org/10.1103/PhysRevC.36.602