Eur. Phys. J. A (2006) 27: 157-165
https://doi.org/10.1140/epja/i2005-10259-y

Nuclear Structure and Reactions

Gamma-ray spectroscopy of the doubly magic nucleus ⁵⁶Ni

¹ Department of Physics, Lund University, S-22100, Lund, Sweden
² School of Chemistry and Physics, Keele University, Keele, UK
³ Physics Division, Argonne National Laboratory, 60439, Argonne, IL, USA
⁴ Chemistry Department, Washington University, 63130, St. Louis, MO, USA
⁵ Nuclear Science Division, Lawrence Berkeley National Laboratory, 94720, Berkeley, CA, USA

^* e-mail: emma.johansson@nuclear.lu.se

Received: 20 December 2005
Accepted: 15 February 2006
Published online: 27 March 2006

Abstract

The doubly magic N = Z nucleus ⁵⁶Ni has been investigated with two fusion-evaporation reactions; ⁴⁰Ca(²⁸Si, 3α)⁵⁶Ni at a beam energy of 122MeV and ²⁸Si(³²S, 2p2n)⁵⁶Ni at 130MeV. To detect γ-rays in coincidence with evaporated particles the Ge-detector array Gammasphere was used in conjunction with the charged-particle detector system, Microball and a 1π neutron detector array. Results include a significantly extended level scheme of ⁵⁶Ni, which is compared to large-scale shell model calculations in the fp shell. The experimental and theoretical results agree to a large extent, with one notable exception; the theoretical model fails to predict the proper sequence of the yrast and yrare 8⁺ states.