Evidence for rigid triaxial deformation at low energy in ${}^{76}$Ge

Excited states of ${}^{76}$Ge have been populated in above-barrier Coulomb excitation and inelastic scattering of a 530-MeV ${}^{76}$Ge beam on a ${}^{238}$U target and studied using in-beam $\gamma$-ray spectroscopy with the Gammasphere array. The $\gamma$ band was extended considerably and one new band was identified. Comparisons of the $\gamma$ band with collective- and shell-model calculations suggest that ${}^{76}$Ge may be a rare example of a nucleus exhibiting rigid triaxial deformation in the low-lying states.

Figure 1

Partial level scheme of ${}^{76}$Ge deduced from the prompt data in this work. Level and transition energies are given in keV. Only those states relevant to the discussion are shown; all are given in Table .

Figure 2

Background-subtracted spectra double gated on (a) the 913- and 1012-keV transitions, and (b) the 948- and 1046-keV transitions in ${}^{76}$Ge.

Figure 3

(a) Experimental staggering $S\left(I\right)$ for isotopes of Ge, Se, and Kr. (b) Experimental staggering in ${}^{76}$Ge compared to the SM and DF-model predictions.