New β-delayed proton decays in the rare-earth region near the proton drip line

The β-delayed proton precursors 125Nd, 128Pm, 129Sm, 137Gd and 139Dy near the proton drip line were produced by the irradiation of 92Mo, 96Ru and 106Cd with an 36Ar 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 β-delayed protons and estimated proton branching ratios to the final states in "daughter" nuclei for the precursors 125Nd, 129Sm, 137Gd and 139Dy, as well as the previously reported ones for the precursors 135Gd and 121Ce, were fitted by a statistical model calculation. The ground-state spins and parities of 121Ce, 125Nd, 129Sm, 135Gd, 137Gd and 139Dy 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 121Ce, 125Nd, 129Sm, 135Gd, 137Gd and 139Dy are highly deformed with β2～0.3.

New β-delayed proton decays in the rare-earth region near the proton drip line

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.