K-mixing in the doubly mid-shell nuclide 170Dy and the role of vibrational degeneracy

P.-A Söderström,A Yagi,N Kurz,Z Patel,I Kojouharov,Zs Podolyák,S Nishimura,J Wu,Zs Vajta,H Schaffner,I Nishizuka,N Inabe,P Lee,S Terashima,S Kanaya,F Browne,N Fukuda,G Lorusso,T Isobe,T Alharbi,A Odahara,I Kuti,S Lalkovski,H Baba,G Lotay,Z Korkulu,P Doornenbal,H Kanaoka,T Kubo,T Sumikama,H Watanabe,E Ideguchi,J J Liu ,D S Ahn ,P H Regan ,E J Lee ,J.j Valiente-Dobón ,Zs Dombrádi ,P M Walker ,C B Moon ,Hiroyuki Takeda ,Xu Fang ,K Y Chae ,G J Lane ,F G Kondev ,Hiroshi Suzuki ,V H Phong ,H L Liu ,Cristina Niță ,C S Lee ,G X Zhang ,R Carroll ,O J Roberts ,C Shand ,A M Bruce ,A Estradé ,C J Griffin ,H Sakuraï ,Z Y Xu

doi:10.1016/j.physletb.2016.09.058

Abstract

A detailed study of the structure of the doubly mid-shell nucleus View the MathML source has been carried out, following isomeric and β decay. We have measured the yrast band up to the spin-parity Jπ=6+ state, the K=2γ -vibration band up to the 5+ state, a low-lying negative-parity band based on a 2− state that could be a candidate for the lowest energy octupole vibration state within this nucleus, and a candidate for the Kπ=6+ two quasi-particle isomer. This state was determined to have an excitation energy of 1643.91(23) keV and a half life of 0.99(4) μs, with a reduced hindrance for its decay to the ground-state band an order of magnitude lower than predicted by NpNn systematics. This is interpreted as being due to γ -vibrational mixing from a near degeneracy of the isomer and the 6+ state of the γ band. Furthermore, the parent nucleus 170Tb has been determined to have a half-life of View the MathML source s with a possible spin-parity of 2−.

Highlights

One of the most successful descriptions of the structure of atomic nuclei is the spherical shell model
Lying precisely in the middle of the closed proton Z = 50, 82 and neutron N = 82, 126 shells, with Z = 66 and N = 104, 170Dy has become a central calibration point for tests of collective as well as single-particle models far from closed shells [1,2,3,4]. What speaks against this simplistic picture are possible deformed and spherical sub-shell closures and other deviations from the smooth systematics that are observed in, for example, 190W [5,6,7] and along the
From γ γ energy coincidences it was determined that the isomeric state mainly decays via the 497 and 386 keV transitions to two intermediate states, the lower of which feeds the 4+ and 2+ states of the yrast band via the 910 and 1076 keV transitions, respectively

Summary

Introduction

One of the most successful descriptions of the structure of atomic nuclei is the spherical shell model. Lying precisely in the middle of the closed proton Z = 50, 82 and neutron N = 82, 126 shells, with Z = 66 and N = 104, 170Dy has become a central calibration point for tests of collective as well as single-particle models far from closed shells [1,2,3,4]. What speaks against this simplistic picture are possible deformed and spherical sub-shell closures and other deviations from the smooth systematics that are observed in, for example, 190W [5,6,7] and along the. The structural and decay properties of this predicted isomer serve as a sensitive test of the structural evolution in the quadrupole deformed

Results

Discussion

Conclusion