Observation of a ${\mathrm{vh}}_{11/2}$ pair alignment in neutron-rich ${}^{118}\mathrm{Pd}$

The yrast band was significantly extended to ${14}^{+}$ and the γ band to $5^{+}$ in neutron-rich ${}^{118}\mathrm{Pd}$ by measuring the γ-γ-γ coincidences emitted from the spontaneous fission of ${}^{252}\mathrm{Cf}$ with Gammasphere. The first band crossing was observed in the yrast band in ${}^{118}\mathrm{Pd}$ at a frequency of ħω≈0.36 MeV at the starting point of the backbending, which is similar to that found in ${}^{112-116}\mathrm{Pd}.$ The first bandbending in the yrast cascade in ${}^{118}\mathrm{Pd}$ is interpreted to be built on a two $h_{11/2}$ neutron configuration based on its similarity to the yrast bands in even-even ${}^{112-116}\mathrm{Pd}.$ Our result indicates ${}^{118}\mathrm{Pd}$ still maintains a prolate shape. The quasineutron Routhian calculations indicate a lower crossing frequency for the $h_{11/2}$ level.