Intruder structures observed in ¹²²Te through inelastic neutron scattering

The excited levels of ¹²²Te to 3.3-MeV excitation have been studied using γ-ray spectroscopy following inelastic neutron scattering. The decay characteristics of these levels have been determined from γ-ray excitation functions, angular distributions at E_n = 1.72, 2.80, and 3.35 MeV, Doppler shifts, and γγ coincidences. Electromagnetic transition rates were deduced for many levels, as were multipole-mixing and branching ratios. Level energies and electromagnetic transition rates were compared to interacting boson model (IBM) calculations, both with and without intruder-state mixing, and to particle-core coupling model calculations. The energies of low-lying levels of ¹²²Te are well described by the IBM with intruder-state mixing calculations, and observed transition rates support emerging intruder bands built on 0⁺ levels. The other models considered do not produce enough low-lying positive parity states; however, U(5) energies to the four quadrupole-phonon level agree very well with observations when states with large intruder configurations are ignored. Mixed-symmetry and quadrupole-octupole excitations have been investigated, but mixing with other configurations and fragmentation of strength prohibit a clear identification of these states.