Triaxiality and the nature of low-energy excitations in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Ge</mml:mi><mml:mprescripts/><mml:none/><mml:mn>76</mml:mn></mml:mmultiscripts></mml:math>
A. D. Ayangeakaa, R. V. F. Janssens, S. Zhu, J. M. Allmond, B. A. Brown, C. Y. Wu, M. Albers, K. Auranen, B. Bucher, M. P. Carpenter, P. Chowdhury, D. Cline, H. L. Crawford, P. Fallon, A. M. Forney, A. Gade, D. J. Hartley, A. B. Hayes, J. Henderson, F. G. Kondev, Krishichayan, T. Lauritsen, J. Li, David Little, A. O. Macchiavelli, D. Rhodes, D. Seweryniak, S. Stolze, W. B. Walters, J. Wu
Abstract
The deformation properties of the low-lying states in $^{76}\mathrm{Ge}$ have been investigated following a safe-energy Coulomb excitation measurement with the GRETINA tracking array and CHICO2 heavy-ion counter at the ATLAS accelerator facility at Argonne National Laboratory. A comprehensive set of transition and static $E2$ matrix elements were extracted from the measured differential Coulomb cross sections and compared with results of configuration-interaction shell-model calculations and computations carried out within the framework of the generalized triaxial rotor model. The remarkable agreement between the calculated and experimental data supports a near-maximum triaxial deformation for the ground state of $^{76}\mathrm{Ge}$. In addition, the degree of softness of the asymmetry in $^{76}\mathrm{Ge}$ and $^{76}\mathrm{Se}$ was investigated using rotational invariants generated from configuration-interaction shell-model wave functions computed with the jj44b and JUN45 effective interactions. The resulting invariants are shown to be consistent with a stiff triaxial deformation in $^{76}\mathrm{Ge}$ and a predominantly soft triaxial potential for $^{76}\mathrm{Se}$, in agreement with the conclusions of recent works by this collaboration.