Level structure of 120Cs Original Research Article

Excited states of the 120Cs nucleus have been studied by using in-beam γ-ray spectroscopy with the 107Ag(16O, 3n)120Cs fusion–evaporation reaction at a beam energy of 85 MeV. The level scheme of 120Cs has been determined using γ–γ coincidence and γ–γ angular correlation analyses. We suggest that the spin of the lowest state for the πh11/2⊗νh11/2 quasiparticle band should be 9+, which is 2ℏ higher in angular momentum than that of previous spin assignment. A spin inversion between the favored and the unfavored states in this positive-parity band was observed below I=19ℏ. In addition, the spin assignment of the negative-parity band with small signature splitting has also been made for the band head with Iπ=8−. These two rotational bands are found to be connected to each other at lower spin states and to the high-spin 7− isomer with half-life of T1/2=61.2 s through different decay paths.