Type II shell evolution in A = 70 isobars from the N ≥ 40 island of inversion

Morales, Ana Isabel; Benzoni, G.; Watanabe, H.; Tsunoda, Y.; Otsuka, Takaharu; Nishimura, S.; Browne, F.; Daido, R.; Doornenbal, P.; Fang, Y.; Lorusso, G.; Patel, Z.; Rice, S.; Sinclair, L.; Söderström, P.-A.; Sumikama, T.; Wu, J.; Xu, Z. Y.; Yagi, A.; Yokoyama, R.; Baba, H.; Avigo, R.; Garrote, F. L. Bello; Blasi, N.; Bracco, A.; Camera, F.; Ceruti, S.; Crespi, F. C. L.; Angelis, G. de; Delattre, M.-C.; Dombrádi, Zs.; Gottardo, A.; Isobe, T.; Kojouharov, I.; Kurz, N.; Kuti, I.; Matsui, K.; Melon, B.; Mengoni, D.; Miyazaki, Takamichi; Modamio-Hoybjor, V.; Momiyama, S.; Napoli, D. R.; Nııkura, M.; Orlandi, R.; Sakuraï, H.; Şahin, E.; Sohler, D.; Schaffner, H.; Taniuchi, R.; Taprogge, J.; Vajta, Zs.; Valiente-Dobón, J.J.; Wieland, O.; Yalçınkaya, M.

doi:10.1016/j.physletb.2016.12.025

Cited by 43 publications

(34 citation statements)

References 42 publications

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“…Further, although the timing requirements in the data analysis strongly favors population in 70 Ni from the short-lived ≈ 100-ms (6 − , 7 − ) level in 70 Co, a small contribution from the longerlived ≈ 500-ms (3 + ) level could be present. We also note that in a recent study of the decay chain 70 Fe→ 70 Co→ 70 Ni by Morales et al [46], it is suggested that the spin/parity of the longer-lived level could be (1 + , 2 + ).…”

Section: Experimental Details and Data Analysismentioning

confidence: 50%

Enhanced low-energy γ-decay strength of Ni70 and its robustness within the shell model

et al. 2018

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Neutron-capture reactions on very neutron-rich nuclei are essential for heavy-element nucleosynthesis through the rapid neutron-capture process, now shown to take place in neutron-star merger events. For these exotic nuclei, radiative neutron capture is extremely sensitive to their γ-emission probability at very low γ energies. In this work, we present measurements of the γ-decay strength of 70 Ni over the wide range 1.3 ≤ E γ ≤ 8 MeV. A significant enhancement is found in the γ-decay strength for transitions with E γ < 3 MeV. At present, this is the most neutron-rich nucleus displaying this feature, proving that this phenomenon is not restricted to stable nuclei. We have performed E1-strength calculations within the quasiparticle time-blocking approximation, which describe our data above E γ 5 MeV very well. Moreover, large-scale shell-model calculations indicate an M1 nature of the low-energy γ strength. This turns out to be remarkably robust with respect to the choice of interaction, truncation and model space, and we predict its presence in the whole isotopic chain, in particular the neutron-rich 72,74,76 Ni.

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Section: Experimental Details and Data Analysismentioning

confidence: 50%

Enhanced low-energy γ-decay strength of Ni70 and its robustness within the shell model

et al. 2018

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“…This phenomenon, widely studied in recent years (see Ref. [11] for a review), may help us to understand the microscopic mechanisms enhancing quantum many-body correlations in exotic nuclei [12][13][14].…”

Section: Introductionmentioning

confidence: 95%

Simultaneous investigation of the T=1(Jπ=0+) and T=0(J

Morales¹,

Algora²,

Rubio³

et al. 2017

Phys. Rev. C

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Simultaneous investigation of the T = 1 (J π = 0 + ) and T = 0 (J π = 9 + ) β decays in The β decay of the odd-odd nucleus 70 Br has been investigated with the BigRIPS and EURICA setups at the Radioactive Ion Beam Factory (RIBF) of the RIKEN Nishina Center. The T = 0 (J π = 9 + ) and T = 1 (J π = 0 + ) isomers have both been produced in in-flight fragmentation of 78 Kr with ratios of 41.6(8)% and 58.4(8)%, respectively. A half-life of t 1/2 = 2157 +53 −49 ms has been measured for the J π = 9 + isomer from γ-ray time decay analysis. Based on this result, we provide a new value of the half-life for the J π = 0 + ground state of 70 Br, t 1/2 = 78.42 ± 0.51 ms, which is slightly more precise, and in excellent agreement, with the best measurement reported hitherto in the literature. For this decay, we provide the first estimate of the total branching fraction decaying through the 2 + 1 state in the daughter nucleus 70 Se, R(2 + 1 ) = 1.3 ± 1.1%. We also report four new low-intensity γ-ray transitions at 661, 1103, 1561, and 1749 keV following the β decay of the J π = 9 + isomer. Based on their coincidence relationships, we tentatively propose two new excited states at 3945 and 4752 keV in 70 Se with most probable spins and parities of J π = (6 + ) and (8 + ), respectively. The observed structure is interpreted with the help of shell-model calculations, which predict a complex interplay between oblate and prolate configurations at low excitation energies.

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“…The resistance-control force, i.e. the monopole interaction, does not promote the collective mode by itself, but can change the "environment" : the ESPEs are optimized to different collective modes giving rise to a large diversity of phenomena [20,21,23,24,37,38,55,56]. Although the CI calculations can be refined, the overall agreement to experiments suggests the validity of the underlying picture, shifting our basic understanding from the Liquid Drop model including its quantized forms to a more explicit multi-nucleon description with aspects such as shape coexistence, triaxial instability and shell evolution.…”

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confidence: 99%

Underlying Structure of Collective Bands and Self-Organization in Quantum Systems

et al. 2019

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The underlying structure of low-lying collective bands of atomic nuclei is discussed from a novel perspective on the interplay between single-particle and collective degrees of freedom, by utilizing state-of-the-art configuration interaction calculations on heavy nuclei. Besides the multipole components of the nucleon-nucleon interaction that drive collective modes forming those bands, the monopole component is shown to control the resistance against such modes. The calculated structure of 154 Sm corresponds to coexistence between prolate and triaxial shapes, while that of 166 Er exhibits a deformed shape with a strong triaxial instability. Both findings differ from traditional views based on β/γ vibrations. The formation of collective bands is shown to be facilitated from a self-organization mechanism.The structure of atomic nuclei exhibits single-particle as well as collective-mode aspects created by the protons and neutrons (nucleons). The former has been characterized by the shell structure shown initially by Mayer [1] and Jensen [2], while the latter has presented a variety of nuclear shapes following Rainwater [3], and Bohr and Mottelson [4][5][6]. The two aspects lead to "the problem of reconciling the simultaneous occurrence of single-particle and collective degrees of freedom ..." [7]. This is one of the most important basic questions in nuclear structure research, and it remains open. For instance, G.E. Brown has addressed the question, "how single particle states can coexist with collective modes", throughout his life [8]. We discuss in this Letter this problem from a novel perspective.Nucleons in an atomic nucleus occupy single-particle orbits in various configurations. The effective nucleonnucleon (NN) interaction in nuclei induces multi-nucleon correlations by mixing such configurations. This mixing occurs, in many cases, basically for "valence" nucleons in single-particle orbits on top of the appropriate closed proton and neutron shell (inert core). The ellipsoidal shapes correspond to such correlations having the nature of quadrupole surface deformation from a sphere, driven by the quadrupole component of the NN interaction [9][10][11][12][13][14]. This gives rise to an interplay between collective mode and single-particle states (SPS's). If SPS's relevant to these correlations are separated by large gaps, the mixing between them and the resulting correlations are reduced. Thus, the SPS's can act as a "resistance" to (the formation of) collective modes. In this Letter, we first present how ellipsoidal shapes emerge from multi-nucleon systems by using the state-of-the-art Configuration Interaction (CI) simulations, called Monte Carlo Shell Model (MCSM) [15,16]. This allowed us to uncover a novel mechanism: the monopole component of the NN interaction shifts the single-particle energies (SPEs) effectively, weakening the "resistance" against deformation, and thus 2 + 4 + a b 0 1 2 E (MeV) N N 0 100 200 B(E2) (W.u.) 4+ calc. 2+ calc. 2+ exp. 4+ exp. -2 -1 0 Q (eb)c N 84 88 92 84 88 92 84 88 92 2+ calc...

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Type II shell evolution in A = 70 isobars from the N ≥ 40 island of inversion

Cited by 43 publications

References 42 publications

Enhanced low-energy γ-decay strength of Ni70 and its robustness within the shell model

Enhanced low-energy γ-decay strength of Ni70 and its robustness within the shell model

Simultaneous investigation of the T=1(Jπ=0+) and T=0(J

Underlying Structure of Collective Bands and Self-Organization in Quantum Systems

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