Configuration and bandhead spin assignments for the 2-quasiparticle rotational bands in the neutron-rich nuclei $^{154, 156}$Pm

Abstract

The rotational bands in the neutron-rich nuclei $^{153-157}$Pm are investigated by a particle-number conserving method. The kinematic moments of inertia for the 1-quasiparticle bands in odd-$A$ Pm isotopes $^{153, 155, 157}$Pm are reproduced quite well by the present calculation. By comparison between the experimental and calculated moments of inertia for the three 2-quasiparticle bands in the odd-odd nuclei $^{154, 156}$Pm, their configurations and bandhead spins have been assigned properly. For the 2-quasiparticle band in $^{154}$Pm, the configuration is assigned as $\pi5/2^-[532]\otimes \nu3/2^-[521]$ ($K^π=4^+$) with the bandhead spin $I_0=4\hbar$. In $^{156}$Pm, the same configuration and bandhead spin assignments have been made for the 2-quasiparticle band with lower excitation energy. The configuration $\pi5/2^+[413]\otimes \nu5/2^+[642]$ ($K^π=5^+$) with the bandhead spin $I_0=5\hbar$ is assigned for that with higher excitation energy.