Observation of $\gamma$-vibrations and alignments built on non-ground-state configurations in 156Dy

Abstract

The exact nature of the lowest $K^{\pi }=2_{\gamma }^{+}$ rotational bands in all deformed nuclei remains obscure. Traditionally they are assumed to be collective vibrations of the nuclear shape in the $\gamma$ degree of freedom perpendicular to the nuclear symmetry axis. Very few such $\gamma$-bands have been traced past the usual back-bending rotational alignments of high-j nucleons. We have investigated the structure of positive-parity bands in the N=90 nucleus 156Dy, using the 148Nd(12C,4n)156Dy reaction at 65 MeV, observing the resulting $\gamma$-ray transitions with the Gammasphere array. The even- and odd-spin members of the $K^{\pi }=2_{\gamma }^{+}$ $\gamma$-band are observed to 32+ and 31+ respectively. This rotational band faithfully tracks the ground-state configuration to the highest spins. The members of a possible $\gamma$-vibration built on the aligned yrast S-band are observed to spins 28+ and 27+. An even-spin positive-parity band, observed to spin 24+, is a candidate for an aligned S-band built on the seniority-zero configuration of the $0_2^{+}$ state at 676 keV. The crossing of this band with the $0_2^{+}$ band is at $\hslash \omega$= 0.28(1) MeV and is consistent with the configuration of the $0_2^{+}$ band not producing any blocking of the monopole pairing.

arXiv commentPublished in Physics Review C

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• Triaxial projected shell model study of gamma-vibrational bands in even-even Er isotopes
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Cited by in corpus (9)

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• Microscopic nuclear structure models and methods : Chiral symmetry, Wobbling motion and $\gamma -$bands
• Quasiparticle and $\gamma$-band structures in ${}^{156}$Dy
• Intrinsic properties of high-spin band structures in triaxial nuclei
• Systematic study of near yrast band structures in odd-mass ${}^{125-137}$Pr and ${}^{127-139}$Pm isotopes
• Shape phase mixing in critical point nuclei
• Extended triaxial projected shell model approach for odd-neutron nuclei
• First candidates for γ vibrational bands built on the [505]11/2- neutron orbital in odd-A Dy isotopes
• Triaxial projected shell model study of $\gamma$-bands in atomic nuclei