Measurements of g-factors of excited states in Ba and Ce nuclei using γ rays from secondary fission fragments

Abstract

Measurements of g-factors of excited states in barium and cerium fission fragments have been performed using time-integral perturbed angular correlations between secondary-fragment γ rays. Larmor precession angles have been obtained for the first I π = 2 + states in 144,146Ba and 146,148Ce as well as for the 9 2 − state at 117 keV in 143Ba, the 7 2 − state at 114 KeV in 145Ba and the first 4 + state in 150Ce. The deduced g-factor for the 2 + state in 146Ba provides substantiating evidence for a downward trend in 2 + g-factors with increasing neutron number, in line with Interacting Boson Model predictions for the neutron-rich barium isotoes, assuming the quenching of the Z = 64 shell gap for N > 88. The static hyperfine fields for implanted barium and cerium isotopes are found to be opposite in sign. These results constitute the first use of secondary-fragment γ-ray emission in the determination of g-factors of excited states in fission fragments.