Observation of Positive-Parity Bands in ${}^{109}$Pd and ${}^{111}$Pd: Enhanced $\gamma$-Softness

Abstract

The neutron-rich nuclei ${}^{109}$Pd and ${}^{111}$Pd were produced as fission fragments following the ${}^{30}$Si + ${}^{168}$Er reaction at 142 MeV. Using the identification based on the coincidences with the complementary fission fragments, the only positive-parity bands observed so far in ${}^{109}$Pd and ${}^{111}$Pd emerged from this work. A band, built on top of the 5/2${}^{+}$ ground state exhibiting $\Delta I$ = 1 energy-level staggering, was observed in each of these nuclei. Both nuclei of interest, ${}^{109}$Pd and ${}^{111}$Pd, are suggested to lie in the transitional region of Pd isotopes of maximum $\gamma$-softness. The ground states of both nuclei are predicted by TRS calculations to be extremely $\gamma$-soft with shallow triaxial minima. The first crossing in the new bands is proposed to be due to an alignment of $h_{11/2}^2$ neutrons.

References in corpus (1)

• Equilibrium shapes and high-spin properties of the neutron-rich A~100 nuclei

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