Excited states in ${}^{110}\mathrm{I}$ have been identified for the first time using the $\alpha \mathrm{pn}$ evaporation channel from the ${}^{58}\mathrm{Ni}{+}^{58}\mathrm{Ni}$ reaction at a beam energy of 250 MeV. The experiment was carried out using GAMMASPHERE coupled to the MICROBALL charged-particle detector array and an array of 15 neutron detectors. Two collective structures were observed with the yrast band built on the $\pi h_{11/2}\otimes \nu h_{11/2}$ configuration. Comparisons of the yrast-band energies with the excitation energies of the yrast states in even ${}_{52}\mathrm{Te}$ and in odd ${}_{52}\mathrm{Te}$ and ${}_{53}\mathrm{I}$ isotopes for $A\sim 110$ were analyzed, revealing different responses of the underlying cores to the valence $\pi h_{11/2}$ and $\nu h_{11/2}$ orbitals. It is concluded that the neutron $h_{11/2}$ valence orbital has a larger influence than that of the proton $h_{11/2}$ valence orbital.

• Received 2 February 2000

DOI:https://doi.org/10.1103/PhysRevC.62.044309