Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Letter
  • Published:

Interplay between nuclear shell evolution and shape deformation revealed by the magnetic moment of 75Cu

Abstract

Exotic nuclei are characterized by having a number of neutrons (or protons) in excess relative to stable nuclei. Their shell structure, which represents single-particle motion in a nucleus1,2, may vary due to nuclear force and excess neutrons3,4,5,6, in a phenomenon called shell evolution7. This effect could be counterbalanced by collective modes causing deformations of the nuclear surface8. Here, we study the interplay between shell evolution and shape deformation by focusing on the magnetic moment of an isomeric state of the neutron-rich nucleus 75Cu. We measure the magnetic moment using highly spin-controlled rare-isotope beams and achieve large spin alignment via a two-step reaction scheme9 that incorporates an angular-momentum-selecting nucleon removal. By combining our experiments with numerical simulations of many-fermion correlations, we find that the low-lying states in 75Cu are, to a large extent, of single-particle nature on top of a correlated 74Ni core. We elucidate the crucial role of shell evolution even in the presence of the collective mode, and within the same framework we consider whether and how the double magicity of the 78Ni nucleus is restored, which is also of keen interest from the perspective of nucleosynthesis in explosive stellar processes.

This is a preview of subscription content, access via your institution

Access options

Rent or buy this article

Prices vary by article type

from$1.95

to$39.95

Prices may be subject to local taxes which are calculated during checkout

Fig. 1: Shell evolution in neutron-rich Cu isotopes.
Fig. 2: Experimental results.
Fig. 3: Systematics of the magnetic moments for odd-A Cu isotopes.
Fig. 4: Theoretical interpretations.

Similar content being viewed by others

Data availability

The data used in the present study are available from the corresponding author upon reasonable request.

References

  1. Mayer, M. G. et al. On closed shells in nuclei. II. Phys. Rev. 75, 1969–1970 (1949).

    Article  ADS  Google Scholar 

  2. Haxel, O., Jensen, J. H. D. & Suess, H. E. On the ‘magic numbers’ in nuclear structure. Phys. Rev. 75, 1766–1766 (1949).

    Article  ADS  Google Scholar 

  3. Warner, D. Not-so-magic numbers. Nature 430, 517–519 (2004).

    Article  ADS  Google Scholar 

  4. Janssens, R. V. F. et al. Unexpected doubly magic nucleus. Nature 459, 1069–1070 (2009).

    Article  ADS  Google Scholar 

  5. Bastin, B. et al. Collapse of the N = 28 shell closure in 42Si. Phys. Rev. Lett. 99, 022503 (2007).

    Article  ADS  Google Scholar 

  6. Steppenbeck, D. et al. Evidence for a new nuclear ‘magic number’ from the level structure of 54Ca. Nature 502, 207–210 (2013).

    Article  ADS  Google Scholar 

  7. Otsuka, T. et al. Evolution of nuclear shells due to the tensor force. Phys. Rev. Lett. 95, 232502 (2005).

    Article  ADS  Google Scholar 

  8. Bohr, A. & Mottelson, B. R. Nuclear Structure (Benjamin, New York, 1969).

    MATH  Google Scholar 

  9. Ichikawa, Y. et al. Production of spin-controlled rare isotope beams. Nat. Phys. 8, 918–922 (2012).

    Article  Google Scholar 

  10. Franchoo, S. et al. Beta decay of 68–74Ni and level structure of neutron-rich Cu isotopes. Phys. Rev. Lett. 81, 3100–3103 (1998).

    Article  ADS  Google Scholar 

  11. Flanagan, K. T. et al. Nuclear spins and magnetic moments of 71,73,75Cu: inversion of π2p 3/2 and π1f 5/2 levels in 75Cu. Phys. Rev. Lett. 103, 142501 (2009).

    Article  ADS  Google Scholar 

  12. Otsuka, T. et al. Novel features of nuclear forces and shell evolution in exotic nuclei. Phys. Rev. Lett. 104, 012501 (2010).

    Article  ADS  Google Scholar 

  13. Petrone, C. et al. Nearly degenerate isomeric states of 75Cu. Phys. Rev. C 94, 024319 (2016).

    Article  ADS  Google Scholar 

  14. Asahi, K. et al. New aspect of intermediate energy heavy ion reactions. large spin polarization of fragments. Phys. Lett. B 251, 488–492 (1990).

    Article  ADS  Google Scholar 

  15. Kubo, T. In-flight RI beam separator BigRIPS at RIKEN and elsewhere in Japan. Nucl. Instrum. Meth. B 204, 97–113 (2003).

    Article  ADS  Google Scholar 

  16. Yano, Y. The RIKEN RI beam factory project: a status report. Nucl. Instrum. Meth. B 261, 1009–1013 (2007).

    Article  ADS  Google Scholar 

  17. Hüfner, J. & Nemes, M. C. Relativistic heavy ions measure the momentum distribution on the nuclear surface. Phys. Rev. C 23, 2538–2547 (1981).

    Article  ADS  Google Scholar 

  18. Talmi, I. Simple Models of Complex Nuclei (CRC Press, Boca Raton, 1990).

    Google Scholar 

  19. Shimizu, N. et al. New-generation Monte Carlo shell model for the K computer era. Prog. Theor. Exp. Phys. 2012, 01A205 (2012).

    Article  Google Scholar 

  20. Otsuka, T. et al. Monte Carlo shell model for atomic nuclei. Prog. Part. Nucl. Phys. 47, 319–400 (2001).

    Article  ADS  Google Scholar 

  21. Tsunoda, Y. et al. Novel shape evolution in exotic Ni isotopes and configuration-dependent shell structure. Phys. Rev. C 89, 031301(R) (2014).

    Article  ADS  Google Scholar 

  22. Otsuka, T. & Tsunoda, Y. The role of shell evolution in shape coexistence. J. Phys. G. Nucl. Part. Phys. 43, 024009 (2016).

    Article  ADS  Google Scholar 

  23. Olivier, L. et al. Persistence of the Z = 28 shell gap around 78Ni: first spectroscopy of 79Cu. Phys. Rev. Lett. 119, 192501 (2017).

    Article  ADS  Google Scholar 

  24. Welker, A. et al. Binding energy of 79Cu: probing the structure of the doubly magic 78Ni from only one proton away. Phys. Rev. Lett. 119, 192502 (2017).

    Article  ADS  Google Scholar 

  25. Hagen, G., Jansen, G. R. & Papenbrock, T. Structure of 78Ni from first-principles computations. Phys. Rev. Lett. 117, 172501 (2016).

    Article  ADS  Google Scholar 

  26. Nowacki, F., Poves, A., Caurier, E. & Bounthong, B. Shape coexistence in 78Ni as the portal to the fifth island of inversion. Phys. Rev. Lett. 117, 272501 (2016).

    Article  ADS  Google Scholar 

  27. Sullivan, C. et al. The sensitivity of core-collapse supernovae to nuclear electron capture. Astrophys. J. 816, 44 (2016).

    Article  ADS  Google Scholar 

  28. Köster, U. et al. In-source laser spectroscopy of 75,77,78Cu: direct evidence for a change in the quasiparticle energy sequence in 75,77Cu and an absence of longer-lived isomers in 78Cu. Phys. Rev. C 84, 034320 (2011).

    Article  ADS  Google Scholar 

  29. Sahin, E. et al. Shell evolution towards 78Ni: low-lying states in 77Cu. Phys. Rev. Lett. 118, 242502 (2017).

    Article  ADS  Google Scholar 

  30. Stone, N. J. et al. Nuclear dipole moment of 71Cu from online β-NMR measurements. Phys. Rev. C 77, 014315 (2008).

    Article  ADS  Google Scholar 

  31. Goldhaber, A. S. Statistical models of fragmentation processes. Phys. Lett. B 53, 306–308 (1974).

    Article  ADS  Google Scholar 

  32. Morinaga, H. & Yamazaki, T. In-Beam Gamma-Ray Spectroscopy (North-Holland, Amsterdam, 1976).

  33. de Groote, R. P. et al. Dipole quadrupole moments of 73–78Cu as a test of the robustness of the Z = 28 shell closure near 78Ni. Phys. Rev. C 96, 041302(R) (2017).

    Article  ADS  Google Scholar 

  34. Wraith, C. et al. Evolution of nuclear structure in neutron-rich odd-Zn isotopes and isomers. Phys. Lett. B 771, 385–391 (2017).

    Article  ADS  Google Scholar 

  35. Castel, B. & Towner, I. S. Modern Theories of Nuclear Moments (Clarendon Press, New York, 1990).

    Google Scholar 

  36. Towner, I. S. Quenching of spin matrix elements in nuclei. Phys. Rep. 155, 263–377 (1987).

    Article  ADS  Google Scholar 

  37. Honma, M., Otsuka, T., Brown, B. A. & Hjorth-Jensen, M. New effective interaction for f 5 pg 9-shell nuclei. Phys. Rev. C 80, 064323 (2009).

    Article  ADS  Google Scholar 

  38. Caurier, E. et al. The shell model as a unified view of nuclear structure. Rev. Mod. Phys. 77, 427–488 (2005).

    Article  ADS  Google Scholar 

  39. Honma, M., Otsuka, T., Brown, B. A. & Mizusaki, T. New effective interaction for pf-shell nuclei and its implications for the stability of the N = Z = 28 closed core. Phys. Rev. C 69, 034335 (2004).

    Article  ADS  Google Scholar 

  40. Stefanescu, I. et al. Interplay between single-particle and collective effects in the odd-A Cu isotopes beyond N = 40. Phys. Rev. Lett. 100, 112502 (2008).

    Article  ADS  Google Scholar 

Download references

Acknowledgements

The experiment was performed under programme no. NP1412-RIBF124R1 at RIBF, operated by RIKEN Nishina Center for Accelerator-Based Science and CNS, The University of Tokyo. The authors thank the RIKEN accelerator staff for their cooperation during the experiment. This work was supported in part by a JSPS KAKENHI grant (16K05390), and also in part by JSPS and CNRS under the Japan-France Research Cooperative Program. The MCSM calculations were performed on the K computer at RIKEN AICS (hp140210, hp150224, hp160211, hp170230). This work was also supported in part by the HPCI Strategic Program (‘The Origin of Matter and the Universe’) and ‘Priority Issue on Post-K computer’ (Elucidation of the Fundamental Laws and Evolution of the Universe). D.L.B., and A.K. acknowledge support by the Extreme Light Infrastructure Nuclear Physics (ELI-NP) Phase II, a project co-financed by the Romanian Government and the European Union through the European Regional Development Fund – the Competitiveness Operational Programme(1/07.07.2016, COP, ID 1334). D.R. was supported by the P2IO Excellence Center.

Author information

Authors and Affiliations

Authors

Contributions

Y.I. designed the experiment, analysed the data and was chiefly responsible for writing the paper. Y.T. and T.O. worked on the theoretical studies, and T.O. helped with writing the paper. The other authors are collaborators on the experiment.

Corresponding author

Correspondence to Y. Ichikawa.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Journal peer review information: Nature Physics thanks Thomas Papenbrock and other anonymous reviewers for their contribution to the peer review of this work.

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Ichikawa, Y., Nishibata, H., Tsunoda, Y. et al. Interplay between nuclear shell evolution and shape deformation revealed by the magnetic moment of 75Cu. Nat. Phys. 15, 321–325 (2019). https://doi.org/10.1038/s41567-018-0410-7

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/s41567-018-0410-7

This article is cited by

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing