We report on a shell model study of ${}^{43}S$ and ${}^{44}S$. Quadrupole rotational invariants proposed by Kumar about 40 years ago allow us to estimate axial and triaxial deformation parameters from shell model calculations. Present results, showing the large impact of the triaxial degree of freedom on the low-lying structure of studied sulfur isotopes, resolve several inconsistencies in previous interpretations of experimental data. In ${}^{43}S$ the prolate ground-state band coexists with a triaxial band built on the 7/2${}_1^{-}$ isomer and an excited prolate structure built on the $K^{\pi }$ = 5/2${}^{-}$ deformed orbit originating from the $\nu f_{7/2}$ shell. In ${}^{44}S$ coexistence of two deformed bands built on mixed 0${}_{1,2}^{+}$ states is reported as well as a pseudo-$\gamma$-band and an excited triaxial structure for which a particle-hole neutron excitation couples to proton collectivity. Present results are in good global agreement with recent antisymmetrized molecular dynamics and beyond-mean-field calculations.

• Received 4 March 2014
• Revised 30 April 2014

DOI:https://doi.org/10.1103/PhysRevC.89.051301