The ${}_{}{}^{184–200}{}_{}{}^{}\mathrm{Hg}$ isotopes are studied in the interacting-boson-approximation-plus-fermion-pair model. In general, energy levels up to I=22 can be reproduced quite well. In the low excitation energy region both the shape evolution and the ($8^{+}$,${10}^{+}$,${12}^{+}$) triplet structure can be reproduced. The ($8^{+}$,${10}^{+}$,${12}^{+}$) triplet structure can be understood as the saturation of isospin 1 fermion-pair interaction at the high spin end. The termination of triplet structure at I=12 strongly supports the (${\mathit{i}}_{13/2}$${)}^2$ band crossing. Striking agreements between the observed energy gaps of (${14}_1^{+}$,${12}_1^{+}$) and ($2_1^{+}$,$0_1^{+}$) states are considered as an indication of weak coupling between the boson core and the fermion pair. The B(E2,I→I-2) are calculated and the spin dependence of the B(E2) values can be reproduced qualitatively. However, the detailed mass dependence is not correctly reproduced.

• Received 21 April 1992

DOI:https://doi.org/10.1103/PhysRevC.46.1682