Identification of deformed intruder states in semi-magic Ni

Chiara, C. J.*; Weisshaar, D.*; Janssens, R. V. F.*; Tsunoda, Yusuke*; Otsuka, Takaharu*; Harker, J. L.*; Walters, W. B.*; Recchia, F.*; Albers, M.*; Alcorta, M.*; Bader, V. M.*; Baugher, T.*; Bazin, D.*; Berryman, J. S.*; Bertone, P. F.*; Campbell, C. M.*; Carpenter, M. P.*; Chen, J.*; Crawford, H. L.*; David, H. M.*; Doherty, D. T.*; Gade, A.*; Hoffman, C. R.*; Homma, Michio*; Kondev, F. G.*; Korichi, A.*; Langer, C.*; Larson, N.*; Lauritsen, T.*; Liddick, S. N.*; Lunderberg, E.*; Macchiavelli, A. O.*; Noji, Shumpei*; Prokop, C. J.*; Rogers, A. M.*; Seweryniak, D.*; Shimizu, Noritaka*; Stroberg, S. R.*; Suchyta, S.*; Utsuno, Yutaka   ; Williams, S.*; Wimmer, K.*; Zhu, S.*

The neutron-rich isotope Ni was produced by multi-nucleon transfer reactions of Zn in the Argonne National Laboratory, and an in-beam -ray experiment were performed using the GRETINA array. The and levels of Ni were observed for the first time. Those levels are regarded as large deformed states associated with proton excitation from the orbit because they cannot be reproduced by a shell-model calculation assuming a small valence space without . A theoretical analysis based on the Monte Carlo shell model published in 2014 indicates that those levels corresponds to a prolate deformed band. The present result demonstrates the occurrence of shape coexistence in neutron-rich Ni isotopes other than a known case of Ni, and confirms the predictive power of the Monte Carlo shell-model calculation.