Ge Yuanxiu

(EC+

Abstract: The (EC+β+) decay of 128Ce was reinvestigated in the 116Sn (16O, 4n) reaction by using a helium-jet tape transport system. The close half-lives of 128Ce and 129Ce made it difficult to separate the decay γ rays of both nuclei apart. Instead of the excitation-function measurements, both reactions of 16O+116Sn and 16O+117Sn were carried out, and from their comparisons, the decay γ rays of 128Ce were clearly told from those of 129Ce. Based on X-γ and γ-γ coincidence measurements, a detailed (EC +β+) decay scheme of 128Ce has been proposed, which revises the previous one.

\beta^{+}

Abstract: The (EC+β+) decay of 128Ce was reinvestigated in the 116Sn (16O, 4n) reaction by using a helium-jet tape transport system. The close half-lives of 128Ce and 129Ce made it difficult to separate the decay γ rays of both nuclei apart. Instead of the excitation-function measurements, both reactions of 16O+116Sn and 16O+117Sn were carried out, and from their comparisons, the decay γ rays of 128Ce were clearly told from those of 129Ce. Based on X-γ and γ-γ coincidence measurements, a detailed (EC +β+) decay scheme of 128Ce has been proposed, which revises the previous one.

) decay study of

The β-delayed proton precursors125Nd128Pm129Sm,137Gd and139Dy near the proton drip line were produced by the irradiation of92Mo,96Ru and106Cd with an36Ar 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,O.55(10)s,2.2(2)s and 0.6 (2)s, respectively. The measured energy spectra of β-delayed protons and estimated proton branching ratios to the final states in “daughter” nuclei for the precursors125Nd,129Sm,137Gd and139Dy, as well as the previously reported ones for the precursors135Gd and121Ce, were fitted by a statistical model calculation. The ground-state spins and parities of121Ce,125Nd,129Sm,139Gd,137Gd and139Dy 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 of121Ce,125Nd,129Sm,135Gd,137Gd and139Dy are highly deformed with β2, - 0.3.

^{128}

The (EC+β+) decay of 128Ce was reinvestigated in the 116Sn (16O, 4n) reaction by using a helium-jet tape transport system. The decay γ rays of 128Ce were unambiguously described from those of 129Ce after taking the comparing experiments of 16O+116Sn and 16O+117Sn. Based on x-γ and γ-γ coincidence measurements, a detailed (EC+β+) decay scheme of 128Ce has been proposed which modifies the previous one, and takes accounts of 100 observed γ-lines.

Ce

The nuclide130Ce was produced by a (16O, 4n) reaction on an enriched118Sn target. Reaction products were transported to a shielded location by using a heliumjet tape transport system. A 22.9 min activity in chemically separated cerium sample was identified as130Ce. The (EC+β+) decay scheme of130Ce was proposed for the first time. This scheme includes 108γ-lines, 107γ-lines among them being new. More than 13 1+ low-lying states of130La are populated in the decay of130Ce. Two new isomers with half-life of 77±10 ns and 17±5 ns were observed by means of delayedγ-γ coincidence measurements.