Beta-decay half-lives of new neutron-rich isotopes of Re, Os and Ir approaching the r-process path near N = 126

Heavy neutron-rich nuclei close to N = 126 were produced by fragmentation of a 1A GeV 208Pb beam at the FRS at GSI. The β-decay half-lives of 7 nuclides have been determined using a novel numerical analysis method. The half-lives of 202,199Ir, 200,199Os and 196Re are reported for the first time. The comparison of the data with model calculations provides indications on the importance of first-forbidden transitions on the β-decay of nuclei around N = 126 and Z < 82

Production and β\beta half-lives of heavy neutron-rich nuclei approaching the r-process path at N=126

Fragmentation reactions of relativistic 238U and 208 Pb projectiles have been used to investigatethe production of heavy neutron-rich nuclei approaching the r-process waiting point at A≈195.The relativistic energies, together with the use of a high resolving-power magnetic spectrometerwere key conditions for the unambiguous identification of nuclei in the region of interest. Usingthis technique we were able to identify 73 new heavy neutron-rich nuclei expanding considerablythe north-west frontier of the chart of nuclide. Moreover, we were able to determine the halflives of 13 of those nuclide. The measured values are signific antly shorter than the predictionsused for r-process model calculations. The confirmation of these results for r-process nuclei atA≈195 would indicate that the r-process at this point is faster than expected, leading to a largerproduction of the heaviest nuclei

Approaching r-process nuclei at N=126

International audienceThe production of heavy neutron-rich nuclei approaching the r-process waiting point at N$\approx$126 has been investigated in fragmentation reactions of relativistic 238U and 208Pb projectiles. Using this technique we were able to identify 73 new heavy neutron-rich nuclei expanding considerably the north-west frontier of the chart of nuclide. Moreover, we were able to determine the half lives of 13 of those nuclides. The measured values are significantly shorter than the predictions used for r-process model calculations. These shorter half lives are understood as due to the role of first-forbidden transitions in the decays of these nuclei. The confirmation of these results for r-process nuclei at N$\approx$126 would indicate that the r-process at this point is faster than expected, leading to a larger production of the heaviest nuclei