Decay of 129Ce to low-lying positive-parity states in 129La

Abstract

Low-lying levels of the 129La isotope have been investigated through the β+/EC decay of 129Ce. The radioactive nuclei were produced in the 94Mo+40Ca reaction at a bombarding energy of 255 MeV and transported with a He-jet system. On-line mass separation was used to select the 129Ce beta-decay γ-γ-t, X- γ- t, e−-γ -t coincidence measurements as well as time multi-analysis were performed. Internal conversion electrons were recorded with a magnetic selector and multipolarities deduced. The level scheme of 129La is discussed and compared with the calculations made in the frame of the neutron-proton Interacting Boson-Fermion Model (IBFM-2).