CERN Accelerating science

Excited states of the isotope 234U were studied employing the one-neutron transfer reaction 235⁢U⁢(𝑑,𝑡)234U at a beam energy of 11 MeV. The reaction channel was selected by an identification of the outgoing tritons in a 𝛥⁢𝐸-𝐸 measurement. In coincidence with the tritons, 𝛾 rays were also detected with the highly efficient MINIBALL spectrometer. Based on the analysis of 𝛾⁢𝛾 coincidence data, the level scheme of 234U was extended. The 4+ state at an energy of 1886.7 keV provides evidence for a possible two-phonon 𝛾⁢𝛾 excitation, which is based on three 𝛾 transitions from this state to the 𝛾 vibrational band. However, this state is populated with a high cross section via the one-neutron transfer reaction, which is not expected for a highly collective excitation. The situation is compared to other known cases from the rare-earth region and to the neighboring isotone 232Th, which so far is the only known case for a two-phonon excitation in the actinide region.