New Beta-Delayed Proton Decays In The Rare-Earth Region Near The Proton Drip Line

The beta-delayed proton precursors Nd-125, Pm-128, Sm-129, Gd-137 and Dy-139 near the proton drip line were produced by the irradiation of Mo-92, Ru-96 and Cd-106 with an Ar-36 beam, and conclusively identified for the first time by using proton-gamma coincidence in combination with a He-jet tape transport system. Their half-lives were determined to be 0.60(15)s,1.0(3)s,0.55(10)s,2.2(2)s and 0.6 (2)s, respectively. The measured energy spectra of beta-delayed protons and estimated proton branching ratios to the final states in "daughter" nuclei for the precursors Nd-125, Sm-129, Gd-137 and Dy-139, as well as the previously reported ones for the precursors Gd-135 and Ce-121, were fitted by a statistical model calculation. The ground-state spins and parities of Ce-121, 125Nd, Sm-129, Gd-135, Gd-137 and Dy-139 were then assigned as 5/2 (+/-),5/2 (+/-), 1/2 (+/-) (or 3/2 (+)),5/2 (+),7/2 (+/-) and 7/2, respectively. The consistency between the experimental spin-parity assignment and the predicted Nilsson diagrams indirectly indicates that the ground states of Ce-121, Nd-125, Sm-129, Gd-135, Gd-137 and Dy-139 and highly deformed with beta(2) similar to 0.3.