Evidence for triaxial shape coexistence in ⁷⁴Ge

The deformation properties of the low-lying states in ⁷⁴Ge have been investigated using multistep Coulomb excitation. The measurements were carried out with the advanced γ -ray tracking array, GRETINA, and the CHICO2 particle detector. A comprehensive set of E2 transition and diagonal matrix elements was deduced following an analysis with the semiclassical coupled-channels code GOSIA. The data were compared with results of calculations carried out within the framework of the generalized triaxial rotor model as well as with the configuration interaction shell model and the symmetric rotor model. Results from calculations with covariant density functional theory were used to construct a five-dimensional collective Hamiltonian for further comparisons with the data. Collectively, the calculations provide an accurate reproduction of the experimental matrix elements and further support an understanding in terms of the coexistence of two axially asymmetric shapes. This leads to an overall interpretation of the underlying structure of ⁷⁴Ge requiring triaxiality, as is also the case in the neighboring even-mass Ge isotopes.