A new γ-decay branch has been found from the well-known 661.659(3)-keV Jπ=11/2-, T1/2=2.552(1) min isomer in Ba137 which is populated in the β decay of Cs137. The new 377.9(3)-keV γ ray connects the isomer to the low-lying 283.5 keV, Jπ=1/2- state. It is of near-pure E5 character. The decay has a γ branching ratio (Brγ=Γγ/Γtot) of 1.12(9)×10-7. The new decay has a B(E5) of 0.71(6) W.u. [B(E5)↓=6.5(6)×105e2fm10], a value consistent with other "single-particle" E5 decays in the region. The new decay branch is of topical interest, as it competes with the much-sought "two-photon" second-order electromagnetic decay from this state.
All Science Journal Classification (ASJC) codes
- Nuclear and High Energy Physics