Evidence for an isomer in 76 Ni

Sawicka, M.; Pfützner, M.; Grzywacz, R.; Daugas, J. M.; Matéa, I.; Lewitowicz, M.; Grawe, H.; Becker, F.; Bélier, G.; Bingham, C. R.; Borcea, R.; Bouchez, E.; Buţă, A.; Drǎgulescu, E.; Sauvestre, J. E.; Георгиев, Г.; Giovinazzo, J.; Hammache, F.; Ibrahim, F.; Mayet, P.; Méot, V.; Negoiţă, F.; Santos, F. de Oliveira; Perru, O.; Roig, O.; Rykaczewski, K. P.; Saint‐Laurent, M. G.; Sorlin, O.; Stănoiu, M.; Stefan, I.; Stödel, C.; Theisen, Ch.; Verney, D.

doi:10.1140/epja/i2002-10333-0

Cited by 24 publications

(11 citation statements)

References 5 publications

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“…We note in passing that the kink at N = 48 in the SM relative excitation energy trend shown in Fig. 3 indicates a return to single-particle behavior at the neutron shell closure N = 50 in agreement with the spherical νg −2 9/2 structure of 76 Ni [27,28].…”

Section: Resultssupporting

confidence: 71%

Low-lying isomeric levels inCu75

Daugas¹,

Faul²,

Grawe

et al. 2010

Phys. Rev. C

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136

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Isomeric low-lying states were identified and investigated in the 75 Cu nucleus. Two states at 61.8(5)-and 128.3(7)-keV excitation energies with half-lives of 370(40)-and 170(15)-ns were assigned as 75m1 Cu and 75m2 Cu, respectively. The measured half-lives combined with the recent spin assignment of the ground state allow one to deduce tentatively spin and parity of the two isomers and the dominant multipolarities of the isomeric transitions with respect to the systematics of the Cu isotopes. Shell-model calculations using an up-to-date effective interaction reproduce the evolution of the 1/2 − , 3/2 − , and 5/2 − states for the neutron-rich odd-mass Cu isotopes when filling the νg 9/2 . The results indicate a significant change in the nuclear structure in this region, where a single-particle 5/2 − state coexists with more and more collective 3/2 − and 1/2 − levels at low excitation energies.

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Section: Resultssupporting

confidence: 71%

Low-lying isomeric levels inCu75

Daugas¹,

Faul²,

Grawe

et al. 2010

Phys. Rev. C

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136

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“…Thus, the Z 28 and N 28 magic structures are weakened or disappear in exotic Ni isotopes. This is also consistent with unusually low-lying 2 levels [20]. Note that the N 28 case is for rather deep hole states and may not be so relevant to lowlying states.…”

supporting

confidence: 80%

Mean Field with Tensor Force and Shell Structure of Exotic Nuclei

2006

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The tensor force is implemented into the mean-field model so that the evolution of nuclear shells can be described for exotic nuclei as well as stable ones. Besides the tensor-force part simulating the meson exchange, the model is an extension of the successful Gogny model. One of the major issues of rareisotope beam physics is a reduced spin-orbit splitting in neutron-rich exotic nuclei. It will be shown that the effect of the tensor force on this splitting is larger than or about equal to the one due to the neutron skin. We will present predictions for stable and exotic nuclei with comparisons to conventional results and experimental data. DOI: 10.1103/PhysRevLett.97.162501 PACS numbers: 21.60.ÿn, 21.10.Pc, 21.30.Fe Like other many-body quantal systems, the mean field governs largely the structure of nuclei. Recently it has been shown, by using the shell model, that the tensor force has a specific, robust, and systematic effect on the single-particle energies of nuclei, even breaking or creating magic numbers in some cases [1]. It is then very interesting to explore what can be seen by including the tensor force into the mean-field calculations. Note that in the shell model, the single-particle wave functions are given a priori and are fixed more or less.The existing successful and systematic mean-field calculations are either of Skyrme-type [2,3] or of Gogny-type [4]. In the former, the interaction is of zero-range nature with derivative couplings, while the tensor terms have been suppressed, probably because the number of free parameters is made as small as possible [5]. In the latter, the interaction is of finite-range nature [4,6,7], while there is no tensor term either.In this Letter, we present a new mean-field model which includes the tensor force explicitly and keeps the merits of the existing models. In exotic nuclei far from stability with large asymmetric ratios between the proton number (Z) and the neutron number (N), the single-particle properties may show distinct characteristic changes from those seen in usual stable nuclei. In particular, in neutron-rich exotic nuclei, the neutron skin can be created [8], which may give rise to a diffuse surface resulting in a reduced spin-orbit splitting [9,10]. The tensor force changes the spin-orbit splitting in a systematic and different way [1]. It should be very important to investigate the neutron-skin effect and the tensor-force effect within a single framework.We introduce a new Gogny-type mean-field model, called GT2. All the terms of the Gogny interaction are kept, while their strength parameters are readjusted. The Gogny interaction contains central interactions with Gaussian-function dependences on the relative distance of nucleons [4,6,7]. Two ranges of Gaussians are included with full four spin-isospin coupling terms, ending up with eight terms. The tensor term is expressed as [1],where 1;2 (s 1;2 ) denotes the isospin (spin) of nucleons 1 and 2, K means the coupling of two operators in the brackets to an angular momentum (or rank) K, and Y d...

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“…76 Ni) [37,38,39,40] and the N = 50 shell strength in Ge isotopes [36]. The inferred 78 Ni shell gaps along with the recently determined empirical T = 1 interaction and single particle (hole) energies for the N = 50 isotones and Ni isotopes [42] provide a new bench mark for tuning the monopole interaction in the 48 Ca to 78 Ni model space.…”

Section: From 48 Ca To 78 Nimentioning

confidence: 95%

“…Early β-decay results seem to indicate a substantial shell quenching [35], while in-beam experiments on N ∼ 50 Ge-Se isotopes [36] and isomer studies following fragmentation [37,38,39,40] give evidence for the persistence of the N = 50 shell. Decisive for both the Z = 28 and N = 50 shell gaps in 78 Ni is according to the tensor force scenario sketched on the right hand side of fig.…”

Section: From 48 Ca To 78 Nimentioning

confidence: 99%

Nuclear structure far off stability --Implications for nuclear astrophysics

Grawe¹,

Blazhev

Górska³

et al. 2006

Eur. Phys. J. A

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Abstract. The single-particle structure and shell gap of 100 Sn as inferred from previous in-beam γ-ray spectroscopy has been confirmed in recent studies of seniority and spin-gap isomers by γγ, βγ, βpγ, pγ and 2pγ spectroscopy. The results for 94,95 Ag, 98 Cd and its N = 50 isotones 96 Pd and 94 Ru stress the importance of large-scale shell model calculations employing realistic interactions for the isomerism, np-nh excitations, seniority mixing and E2 polarisation of the 100 Sn core. The strong monopole interaction of the ∆l = 0, 1 spin/isospin-flip partners πg 9/2 -νg 7/2 along the N = 50 isotones and the πf 5/2 -νg 9/2 pair of nucleons along the Z = 28 Ni isotopes are decisive for the evolution of the shell structure towards 100 Sn and 78 Ni. It can be traced back to the tensor force in the effective nucleon-nucleon interaction and provides a straightforward explanation for new shells in neutron-rich light nuclei, implying qualitative predictions for new N = 32, 34 subshells in Ca isotopes, persistence of the 78 Ni proton and neutron shell gaps and non-equivalence of the g 9/2 valence mirror Ni isotopes and N = 50 isotones. This is corroborated by recent experimental data on 56,58 Cr and 70-76 Ni. The implication of monopole driven shell evolution for apparent spin-orbit splitting towards N Z and structure along the astrophysical r-path between N = 50 and N = 82 is discussed.

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Evidence for an isomer in 76 Ni

Cited by 24 publications

References 5 publications

Low-lying isomeric levels inCu75

Low-lying isomeric levels inCu75

Mean Field with Tensor Force and Shell Structure of Exotic Nuclei

Nuclear structure far off stability --Implications for nuclear astrophysics

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