Characterization of the shape-staggering effect in mercury nuclei

Bruce A Marsh, Thomas Day Goodacre, Simon Sels, Y. Tsunoda, B. Andel, Andrei N. Andreyev, N. A. Althubiti, Dimitar Atanasov, A. E. Barzakh, J. Billowes, Klaus Blaum, Thomas Elias Cocolios, Cubiss James G., J. Dobaczewski, G.J. Farooq-Smith, D.V. Fedorov, Valentin N. Fedosseev, K.T. Flanagan, Liam Paul Gaffney, Lars GhysMark Huyse, S. Kreim, David Lunney, Kara M Lynch, Vladimir Manea, Yisel Martinez, P.L. Molkanov, T. Otsuka, A. Pastore, M. Rosenbusch, Ralf Erik Rossel, Sebastian Rothe, Lutz Schweikhard, Maxim Seliverstov, P. Spagnoletti, Celine Van Beveren, Piet Van Duppen, M. Veinhard, Verstraelen Elise, A. Welker, K. Wendt, Frank Wienholtz, R.N. Wolf, Alexandra Zadvornaya, Kai Zuber

    Research outputpeer-review


    In rare cases, the removal of a single proton (Z) or neutron (N) from an atomic nucleus leads to a dramatic shape change. These instances are crucial for understanding the components of the nuclear interactions that drive deformation. The mercury isotopes (Z = 80) are a striking example1,2: their close neighbours, the lead isotopes (Z = 82), are spherical and steadily shrink with decreasing N. The even-mass (A = N + Z) mercury isotopes follow this trend. The odd-mass mercury isotopes 181,183,185Hg, however, exhibit noticeably larger charge radii. Due to the experimental difficulties of probing extremely neutron-deficient systems, and the computational complexity of modelling such heavy nuclides, the microscopic origin of this unique shape staggering has remained unclear. Here, by applying resonance ionization spectroscopy, mass spectrometry and nuclear spectroscopy as far as 177Hg, we determine 181Hg as the shape-staggering endpoint. By combining our experimental measurements with Monte Carlo shell model calculations, we conclude that this phenomenon results from the interplay between monopole and quadrupole interactions driving a quantum phase transition, for which we identify the participating orbitals. Although shape staggering in the mercury isotopes is a unique and localized feature in the nuclear chart, it nicely illustrates the concurrence of single-particle and collective degrees of freedom at play in atomic nuclei.
    Original languageEnglish
    Pages (from-to)1-6
    Number of pages6
    JournalNature Physics
    StatePublished - 1 Oct 2018

    Cite this