Unusual neutron-capture gamma-ray cascade in 124Te: A fingerprint of octupole-coupled multiphonon states

Abstract The properties of the special levels in 124 Te that are strongly populated by thermal neutron-capture γ-rays have been determined with 123 Te(n,γ) and 124 Te(γ,γ′) experiments. The unusual decay pattern can be consistently explained within the quasiparticle-phonon model assuming a three-phonon |2 1 + ⊗ 2 1 + ⊗ 3 1 − ; 2 − 〉 configuration of the upper intermediate level at 3.101 MeV which exclusively decays to a close-lying two-phonon |2 1 + ⊗ 3 1 f- ; 1 f- f> state at 2.747 MeV. The (γ,γf') reaction strongly excites the latter and also indicates the 1 f- member of the three-phonon 2 1 + ⊗ 2 1 + ⊗ 3 1 f- septuplet at 3.091 MeV.