High-spin spectroscopy ofI119,121: Prolate and oblate shape coexistence

High-spin states in the odd-proton ${}_{}{}^{119,121}{}_{}{}^{}\mathrm{I}$ isotopes have been studied following heavy-ion fusion-evaporation reactions using boron and carbon beams. Both prolate (γ=0°) and oblate (γ=-60°) collective bands have been observed built on low-lying positive- and negative-parity proton states, namely, ${\mathit{h}}_{11/2}$, ${\mathit{g}}_{9/2}$, ${\mathit{g}}_{7/2}$, and ${\mathit{d}}_{5/2}$ orbitals. At the highest spins (∼39/2) the collective behavior of the ${\mathit{h}}_{11/2}$ yrast band is seen to break down when noncollective oblate states become yrast, resulting in the observation of band termination. The terminating state involves the π${\mathit{h}}_{11/2}$⊗[π${\mathit{g}}_{7/2}$ ${]}^2$⊗[ν${\mathit{h}}_{11/2}$ ${]}^2$ configuration at γ=+60°.