High-K isomer and the rotational properties in the odd-Z neutron-rich nucleus ${}^{163}$Eu

Abstract

The newly observed isomer and ground-state band in the odd-Z neutron-rich rare-earth nucleus ${}^{163}$Eu are investigated by using the cranked shell model (CSM) with pairing treated by the particle-number conserving (PNC) method. This is the first time detailed theoretical investigations are performed of the observed $964(1)$ keV isomer and ground-state rotational band in ${}^{163}$Eu. The experimental data are reproduced very well by the theoretical results. The configuration of the $964(1)$ keV isomer is assigned as the three-particle state ${\frac{13}{2}}^{-}(\nu {\frac{7}{2}}^{+}[633]\otimes \nu {\frac{1}{2}}^{-}[521]\otimes \pi {\frac{5}{2}}^{+}[413]$). More low-lying multi-particle states are predicted in ${}^{163}$Eu. Due to its significant effect on the nuclear mean field, the high-order ${\epsilon }_6$ deformation plays an important role in the energy and configuration assignment of the multi-particle states. Compared to its neighboring even-even nuclei ${}^{162}$Sm and ${}^{164}$Gd, there is a $10\%\sim 15\%$ increase of $J^{(1)}$ of the one-particle ground-state band in ${}^{163}$Eu. This is explained by the pairing reduction due to the blocking of the nucleon on the proton $\pi {\frac{5}{2}}^{+}$[413] orbital in ${}^{163}$Eu.