Ultrafast-timing lifetime measurements in 
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Ru</mml:mi><mml:mprescripts /><mml:none /><mml:mn>94</mml:mn></mml:mmultiscripts></mml:math>
 and 
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Pd</mml:mi><mml:mprescripts /><mml:none /><mml:mn>96</mml:mn></mml:mmultiscripts></mml:math>
: Breakdown of the seniority scheme in 
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Mach, H.; Korgul, A.; Górska, M.; Grawe, H.; Matéa, I.; Stănoiu, M.; Fraile, L. M.; Penionzkevich, Yu. E.; Santos, F. de Oliviera; Verney, D.; Cederwall, B.; Covello, A.; Dlouhý, Z.; Fogelberg, B.; Gargano, A.; Георгиев, Г.; Grzywacz, R.; Lisetskiy, A. F.; Mrázek, J.; Nowacki, F.; Płóciennik, W.; Podolyák, Zs.; Ray, S.; Ruchowska, E.; Saint‐Laurent, M. G.; Sawicka, M.; Stödel, C.; Tarasov, O.

doi:10.1103/physrevc.95.014313

Cited by 31 publications

(45 citation statements)

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“…5 gives us an unique opportunity to understand the 4 + → 2 + E2 transitions of 96 Pd and 94 Ru as measured in Ref. [37,38]: The E2 transition in 96 Pd corresponds to a vanishing 4 + v =2 → 2 + v =2 transition seen in right-hand side of Fig. 5 while the large E2 transition in 94 Ru indicates that the nucleus is indeed located in the transitional region where the transition strength is very sensitive to the mixture of the two configurations.…”

Section: Have Done Calculations With Different Effective Interactiomentioning

confidence: 97%

Partial conservation of seniority and its unexpected influence on E2 transitions in g 9/2 nuclei

2017

Physics Letters B

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There exist two uniquely defined v = 4 states in systems within a j = 9/2 subshell, which automatically conserve seniority and do not mix with other states. Here I show that the partial conservation of seniority plays an essential role in our understanding of the electric quadrupole transitions of the semimagic nuclei involving j = 9/2 subshells, including the long-lived 8 + isomer in 94 Ru. The effects of configuration mixing from neighboring subshells on the structure of those unique states are analysed. It is shown that a sharp transition from pure seniority coupling to a significant mixture between the v = 2 and v = 4 states may be induced by the cross-orbital nondiagonal interaction matrix elements. Such strong mixture is essential to explain the observed E2 transition properties of N = 50 isotones 96 Pd and 94 Ru.PACS numbers: 21.10. Tg, 21.60.Cs,27.60.+j One of the greatest challenges in nuclear physics is to understand the regular and simple patterns that emerge from the complex nuclear structure. Among those one can mention the shell structure as a consequence of the strong spin-orbit coupling, which is characterized by nucleons occupying orbitals with different lj values. While the original shell model is mostly built upon independent particle motion, the concept of seniority symmetry has been applied implicitly to account for the strong pairing correlation. The seniority quantum number refers to the minimum number of unpaired particles in a single-j shell for a given configuration |j n ; I with total angular momentum I [1]. The seniority coupling has shown remarkable success in describing the spectroscopy and electromagnetic transition properties of semi-magic nuclei restricted to a single j shell. Of particular interest are nuclei that can be well approximated by the seniority coupling in high j orbitals like 0f 7/2 . For heavier systems, we can mention the neutron-rich 70−78 Ni isotopes [2], the N = 50 and 82 [3] isotones in the 0g 9/2 proton subshell, neutron-rich isotopes 134−140 Sn with in the 1f 7/2 subshell [4] as well as 210−218 Pb in the 1g 9/2 neutron subshell [5].Seniority remains a good quantum number within a subshell when j ≤ 7/2. All states in such systems can be uniquely specified by the total angular momentum I and seniority v. The interaction matrix elements have to satisfy a number of constraints in order to conserve seniority when j > 7/2. For a subshell with j = 9/2, where all but one two-body matrix elements conserve seniority, the condition reads [1, 6-10]where V J = j 2 ; J|V |j 2 ; J denotes a two-body matrix element and J the angular momentum of a two-particle * chongq@kth.se state |j 2 . The symmetry is broken for most effective interactions (see, e.g., Ref.[11]) in subshells with j ≥ 9/2 where the eigenstates would be admixtures of states with different seniorities. For a system with n = 4 identical fermions in a j = 9/2 shell, there are three I = 4 (and also I = 6) states, which may be constructed so that one state has seniority v = 2 and the other two have seniority v =...

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Section: Have Done Calculations With Different Effective Interactiomentioning

confidence: 97%

Partial conservation of seniority and its unexpected influence on E2 transitions in g 9/2 nuclei

2017

Physics Letters B

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“…In table IV of the supplementary material one can see that the best, although still poor agreement with the experimental ratio R is found for MCSM, the only calculation including the full proton f pg 9/2 d 5/2 model space and the neutron d 5/2 shell above N = 50. Similarly, the hindrance of the 4 + (υ = 2) → 2 + (υ = 2) transition in the valence-mirror-symmetry nucleus 96 Pd has been attributed to core excitations across N = 50 [29].…”

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confidence: 98%

“…The recent measurement of key experimental observables such as the energy of the yrast 8 + state and the lifetime of the 4 + 1 level in 72 Ni [27,28] supports this explanation. In spite of the great advances, the question regarding the conservation of seniority as a good quantum number for close-lying levels with equal total spin J is still under debate [29,30].…”

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Is seniority a partial dynamic symmetry in the first νg9/2 shell?

et al. 2018

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The low-lying structures of the midshell νg 9/2 Ni isotopes 72 Ni and 74 Ni have been investigated at the RIBF facility in RIKEN within the EURICA collaboration. Previously unobserved low-lying states were accessed for the first time following β decay of the mother nuclei 72 Co and 74 Co. As a result, we provide a complete picture in terms of the seniority scheme up to the first (8 + ) levels for both nuclei. The experimental results are compared to shell-model calculations in order to define to what extent the seniority quantum number is preserved in the first neutron g 9/2 shell. We find that the disappearance of the seniority isomerism in the (8 + 1 ) states can be explained by a lowering of the seniority-four (6 + ) levels as predicted years ago. For 74 Ni, the internal de-excitation pattern of the newly observed (6 + 2 ) state supports a restoration of the normal seniority ordering up to spin J = 4. This property, unexplained by the shell-model calculations, is in agreement with a dominance of the single-particle spherical regime near 78 Ni.

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“…Particularly important is the conservation of the seniority quantum number υ -the number of protons or neutrons that are not coupled in pairs to J = 0 [33,34]-as it is a good indicator of gap stability. In the Ni nuclei filling the νg 9/2 shell, the seniority is still a good quantum number for a sub-set of solvable eigenstates [35][36][37][38][39][40], although it is still unknown if the deformationdriving forces might induce mixing of seniorities in closelying states with equal J [11,41,42].…”

Section: Introductionmentioning

confidence: 99%

Persistence of the Z=28 shell gap in A=75 isobars: Identification of a possible (1/2
Escrig¹,
Morales²,
Nishimura³
et al. 2021
Phys. Rev. C
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Background: The evolution of shell structure around doubly-magic exotic nuclei is of great interest in nuclear physics and astrophysics. In the 'south-west' region of 78 Ni, the development of deformation might trigger a major shift in our understanding of explosive nucleosynthesis. To this end, new spectroscopic information on key close-lying nuclei is very valuable.Purpose: We intend to measure the isomeric and β decay of 75 Co, with one proton-and two neutron-holes relative to 78 Ni, to access new nuclear structure information in 75 Co and its β-decay daughters 75 Ni and 74 Ni.Methods: The nucleus 75 Co is produced in relativistic in-flight fission reactions of 238 U at the Radioactive Ion Beam Factory (RIBF) in the RIKEN Nishina Center. Its isomeric and β decay are studied exploiting the BigRIPS and EURICA setups.Results: We obtain partial β-decay spectra for 75 Ni and 74 Ni, and report a new isomeric transition in 75 Co. The energy (Eγ = 1914(2) keV) and half-life (t 1/2 = 13(6) µs) of the delayed γ ray lend support for the existence of a J π = (1/2 − ) isomeric state at 1914(2) keV. A comparison with PFSDG-U shell-model calculations provides good account for the observed states in 75 Ni, but the first calculated 1/2 − level in 75 Co, a prolate K = 1/2 state, is predicted about 1 MeV below the observed (1/2 − ) level.Conclusions: The spherical-like structure of the lowest-lying excited states in 75 Ni is proved. In the case of 75 Co, the results suggest that the dominance of the spherical configurations over the deformed ones might be stronger than expected below 78 Ni. Further experimental efforts to discern the nature of the J π = (1/2 − ) isomer are necessary.

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Ultrafast-timing lifetime measurements in Ru94 and Pd96 : Breakdown of the seniority scheme in <

Cited by 31 publications

References 38 publications

Partial conservation of seniority and its unexpected influence on E2 transitions in g 9/2 nuclei

Partial conservation of seniority and its unexpected influence on E2 transitions in g 9/2 nuclei

Is seniority a partial dynamic symmetry in the first νg9/2 shell?

Persistence of the Z=28 shell gap in A=75 isobars: Identification of a possible (1/2
Escrig¹,
Morales²,
Nishimura³
et al. 2021
Phys. Rev. C
Self Cite
3
0
2
0
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Ultrafast-timing lifetime measurements in Ru94 and Pd96 : Breakdown of the seniority scheme in <

Cited by 31 publications

References 38 publications

Partial conservation of seniority and its unexpected influence on E2 transitions in g 9/2 nuclei

Partial conservation of seniority and its unexpected influence on E2 transitions in g 9/2 nuclei

Is seniority a partial dynamic symmetry in the first νg9/2 shell?

Persistence of the Z=28 shell gap in A=75 isobars: Identification of a possible (1/2Escrig1, Morales2, Nishimura3 et al. 2021Phys. Rev. CSelf Cite3020View full textAdd to dashboardCite

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Persistence of the Z=28 shell gap in A=75 isobars: Identification of a possible (1/2
Escrig¹,
Morales²,
Nishimura³
et al. 2021
Phys. Rev. C
Self Cite
3
0
2
0
View full text Add to dashboard Cite