$^{78}$Ni revealed as a doubly magic stronghold against nuclear deformation
Abstract
Nuclear magic numbers, which emerge from the strong nuclear force based on quantum chromodynamics, correspond to fully occupied energy shells of protons, or neutrons inside atomic nuclei. Doubly magic nuclei, with magic numbers for both protons and neutrons, are spherical and extremely rare across the nuclear landscape. While the sequence of magic numbers is well established for stable nuclei, evidence reveals modifications for nuclei with a large proton-to-neutron asymmetry. Here, we provide the first spectroscopic study of the doubly magic nucleus Ni, fourteen neutrons beyond the last stable nickel isotope. We provide direct evidence for its doubly magic nature, which is also predicted by ab initio calculations based on chiral effective field theory interactions and the quasi-particle random-phase approximation. However, our results also provide the first indication of the breakdown of the neutron magic number 50 and proton magic number 28 beyond this stronghold, caused by a competing deformed structure. State-of-the-art phenomenological shell-model calculations reproduce this shape coexistence, predicting further a rapid transition from spherical to deformed ground states with Ni as turning point.
Keywords
Cite
@article{arxiv.1912.05978,
title = {$^{78}$Ni revealed as a doubly magic stronghold against nuclear deformation},
author = {R. Taniuchi and C. Santamaria and P. Doornenbal and A. Obertelli and K. Yoneda and G. Authelet and H. Baba and D. Calvet and F. Château and A. Corsi and A. Delbart and J. -M. Gheller and A. Gillibert and J. D. Holt and T. Isobe and V. Lapoux and M. Matsushita and J. Menéndez and S. Momiyama and T. Motobayashi and M. Niikura and F. Nowacki and K. Ogata and H. Otsu and T. Otsuka and C. Péron and S. Péru and A. Peyaud and E. C. Pollacco and A. Poves and J. -Y. Roussé and H. Sakurai and A. Schwenk and Y. Shiga and J. Simonis and S. R. Stroberg and S. Takeuchi and Y. Tsunoda and T. Uesaka and H. Wang and F. Browne and L. X. Chung and Z. Dombradi and S. Franchoo and F. Giacoppo and A. Gottardo and K. Hadyńska-Klęk and Z. Korkulu and S. Koyama and Y. Kubota and J. Lee and M. Lettmann and C. Louchart and R. Lozeva and K. Matsui and T. Miyazaki and S. Nishimura and L. Olivier and S. Ota and Z. Patel and E. Şahin and C. Shand and P. -A. Söderström and I. Stefan and D. Steppenbeck and T. Sumikama and D. Suzuki and Z. Vajta and V. Werner and J. Wu and Z. Y. Xu},
journal= {arXiv preprint arXiv:1912.05978},
year = {2019}
}