High-spin structure ofTl189: Role ofh9/2protons in the prolate minimum of light Hg isotopes

High-spin states in ${}_{}{}^{189}{}_{}{}^{}\mathrm{Tl}$ have been populated through the ${}_{}{}^{165}{}_{}{}^{}\mathrm{Ho}$ ${(}^{28}$Si,4n) reaction and studied with in-beam γ-ray spectroscopy techniques. Both oblate and prolate structures associated with the i13/2 proton orbit are confirmed and extended to higher spins (19/2 and 41/2, respectively). However, only the oblate structure related to the πh9/2 has been observed meaning that the associated prolate structure is nonyrast contrary to expectation. This experimental result points clearly to a large amplitude of (πh9/2${)}^2$ in the wave function of the prolate minimum of ${}_{}{}^{188}{}_{}{}^{}\mathrm{Hg}$.