Observation of γ vibrations and alignments built on non-ground-state configurations in Dy156

Abstract : The exact nature of the lowest Kπ=2+ rotational bands in all deformed nuclei remains obscure. Traditionally they are assumed to be collective vibrations of the nuclear shape in the γ degree of freedom perpendicular to the nuclear symmetry axis. Very few such γ bands have been traced past the usual backbending rotational alignments of high-j nucleons. We have investigated the structure of positive-parity bands in the N=90 nucleus Dy156, using the Nd148(C12,4n)Dy156 reaction at 65 MeV, observing the resulting γ-ray transitions with the Gammasphere array. The even- and odd-spin members of the Kπ=2+γ band are observed up to 32+ and 31+, respectively. This rotational band faithfully tracks the ground-state configuration to the highest spins. The members of a possible γ vibration built on the aligned yrast S band are observed up to spins 28+ and 27+. An even-spin positive-parity band, observed up 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 ℏωc=0.28(1)MeV and is consistent with the configuration of the 0+2 band not producing any blocking of the monopole pairing.
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Physical Review C, American Physical Society, 2015, 91, pp.034330. 〈10.1103/PhysRevC.91.034330〉
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Soumis le : lundi 27 avril 2015 - 15:33:32
Dernière modification le : jeudi 15 mars 2018 - 11:40:08

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S.N.T. Majola, D.J. Hartley, L.L. Riedinger, J.F. Sharpey-Schafer, J.M. Allmond, et al.. Observation of γ vibrations and alignments built on non-ground-state configurations in Dy156. Physical Review C, American Physical Society, 2015, 91, pp.034330. 〈10.1103/PhysRevC.91.034330〉. 〈in2p3-01146046〉

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