Shape coexistence and the role of axial asymmetry in $^{72}$Ge

Authors :: Ayangeakaa, A. D.
Janssens, R. V. F.
Wu, C. Y.
Allmond, J. M.
Wood, J. L.
Zhu, S.
Albers, M.
Almaras-Calderon, S.
Bucher, B.
Carpenter, M. P.
Chiara, C. J.
Cline, D.
Crawford, H. L.
David, H. M.
Harker, J.
Hayes, A. B.
Hoffman, C. R.
Kay, B. P.
Kolos, K.
Korichi, A.
Lauritsen, T.
Macchiavelli, A. O.
Richard, A.
Seweryniak, D.
Wiens, A.
Source :: Phys. Lett. B 754, 254 (2016)
Publication Year :: 2016
Abstract: The quadrupole collectivity of low-lying states and the anomalous behavior of the $0^+_2$ and $2^+_3$ levels in $^{72}$Ge are investigated via projectile multi-step Coulomb excitation with GRETINA and CHICO-2. A total of forty six $E2$ and $M1$ matrix elements connecting fourteen low-lying levels were determined using the least-squares search code, gosia. Evidence for triaxiality and shape coexistence, based on the model-independent shape invariants deduced from the Kumar-Cline sum rule, is presented. These are interpreted using a simple two-state mixing model as well as multistate mixing calculations carried out within the framework of the triaxial rotor model. The results represent a significant milestone towards the understanding of the unusual structure of this nucleus.<br />Comment: 7 pages and 7 figures