Proton-neutron multiplet states and isomers in the odd-odd nucleus 122i

The level structure of the odd-odd iodine nucleus 122I has been studied by the 120Sn (7Li,5n)122I reaction at Elab=58 MeV. Two chopped beams from the 14UD (Unit Doubled) tandem heavy-ion accelerator at the Australian National University were used; one was a nanosecond (ns) pulsed-beam with separation of 1.7 microseconds (μs) and the second one was a 60−μs beam separated by 880 μs. Through in-beam and out-of-beam γ-ray spectroscopy, the complex proton-neutron multiplet states, including isomers with half-lives of a few tens of ns to a few tens of μs, have been identified. Collective states based on the proton h11/2 orbital exhibit two kinds of structure depending upon the coupled neutron orbital: a quadrupole vibration when involving the h11/2 orbital and aγ-soft deformed rotation when involving the g7/2 orbital. With spherical shell model and deformed shell-model calculations, the observed level structures are explained.This work was supported by the Rare Isotope Science Project (RISP) of the Institute for Basic Science (IBS) funded by the Ministry of Science, ICT and Future Planning (MSIP) and by the National Research Foundation (NRF) of the Republic of Korea (Grant No. 2013M7A1A1075764). This work was also supported by the National Research Foundation (NRF) of the Republic of Korea grant funded by the Ministry of Science, ICT and Future Planning (MSIP) (Grant No. 2018R1A5A1025563) and the National Natural Science Foundation of China (Grant No. 11775316)