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

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

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

Date

2016-10-26

Authors

Söderström, P.-A.

Walker, P.M.

Wu, J.

Liu, H.L.

Regan, P.H.

Watanabe, H.

Doornenbal, P.

Korkulu, Z.

Lee, P.

Liu, J.J.

Publisher

Elsevier

Abstract

A detailed study of the structure of the doubly mid-shell nucleus ¹⁷⁰₆₆Dy₁₀₄ 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=2 γ -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 0.91(ˍ₁₃⁺¹⁸)s with a possible spin-parity of 2¯.