Production Of Heavy Neutron-rich Nuclei Research Articles

Optimal condition for the production of heavy and superheavy neutron-rich isotopes with multinucleon transfer reaction

Production cross sections of multinucleon transfer reactions are systematically investigated in the framework of the improved DNS model combined with statistical GEMINI++ model. The calculated isotone distribution of final products in 20 reaction systems at collision energies above the Coulomb barrier are roughly in agreement with experimental data for a wide range of transfers, respectively, especially in the distribution trend. One founds that the combinations of actinide projectiles or larger neutron excess radioactive projectiles and 208Pb or 198Pt targets at energies near the Coulomb barrier can be considered for future experiments on the production of heavy neutron-rich nuclei.

Role of neutron excess in the projectile for the production of heavy neutron-rich nuclei

To shed light on the conditions for synthesizing some new heavy neutron-rich nuclei using multinucleon transfer reactions, the reaction systems $^{40}\mathrm{Ca}+^{208}\mathrm{Pb}$, $^{58}\mathrm{Ni}+^{208}\mathrm{Pb}$, $^{40}\mathrm{Ar}+^{208}\mathrm{Pb}$, $^{64}\mathrm{Ni}+^{208}\mathrm{Pb}$, and $^{136}\mathrm{Xe}+^{208}\mathrm{Pb}$ are investigated within improved dinuclear system (DNS) $\mathrm{model}+$gemini$++$. The transfer cross sections are calculated and compared with existing experimental data. The calculated results are in good agreement with available data. One found the projectiles are changed from the neutron-deficient $^{40}\mathrm{Ca}$ and $^{58}\mathrm{Ni}$ to moderately neutron-rich $^{40}\mathrm{Ar}$, and neutron-rich $^{64}\mathrm{Ni}$ and $^{136}\mathrm{Xe}$ projectiles on $^{208}\mathrm{Pb}$ target, the transfer flux its trend gradually evolves from proton stripping and neutron pickup to the proton pickup and neutron stripping and pickup (pickup and stripping are referring to the projectilelike fragment).

Production of heavy neutron-rich nuclei with radioactive beams in multinucleon transfer reactions

The production mechanism of heavy neutron-rich nuclei is investigated by using the multinucleon transfer reactions of $$^{136,148}{\hbox {Xe}}+^{208}$$ Pb and $$^{238}{\hbox {U}}+^{208}$$ Pb in the framework of a dinuclear system model. The evaporation residual cross sections of target-like fragments are studied with the reaction system $$^{148}{\hbox {Xe}}+^{208}$$ Pb at near barrier energies. The results show that the final isotopic production cross sections in the neutron-deficient side are very sensitive to incident energy while it is not sensitive in the neutron-rich side. Comparing the isotopic production cross sections for the reactions of $$^{208}$$ Pb bombarded with stable and radioactive projectiles, we find that neutron-rich radioactive beams can significantly increase the production cross sections of heavy neutron-rich nuclei.

Production of neutron-rich isotopes around N=126 in multinucleon transfer reactions

The multinucleon transfer reactions has been investigated within the dinuclear system model. The nucleon transfer is coupled to the dissipation of relative motion energy and angular momentum by solving a set of microscopically derived master equations. A barrier distribution approach is implemented in the model in order to including the contributions of different orientations and dynamical effects. The available data of fragment production via multinucleon transfer reactions could be understood with the model for the reactions of $^{136}$Xe + $^{198}$Pt/$^{208}$Pb near Coulomb barrier energies. It is found that the production of heavy neutron-rich nuclei weakly depends on the incident energy. However, the yields of proton-rich nuclei increase with the incident energy.

Production of heavy neutron-rich nuclei in transfer reactions within the dinuclear system model

The dynamics of nucleon transfer processes in heavy-ion collisions is investigated within the dinuclear system model. The production cross sections of nuclei in the reactions 136Xe+208Pb and 238U+248Cm are calculated, and the calculations are in good agreement with the experimental data. The transfer cross sections for the 58Ni+208Pb reaction are calculated and compared with the experimental data. We predict the production cross sections of neutron-rich nuclei Eu, Tb, Ho, and based on the reaction 176Yb+238U. It can be seen that the production cross sections of the neutron-rich nuclei 165Eu, 169Tb, 173Ho, and 181Yb are 2.84 μb, 6.90 μb, 46.24 μb, and 53.61 μb, respectively, which could be synthesized in experiment.

Approaching r-process nuclei at N = 126

The production of heavy neutron-rich nuclei approaching the r-process waiting point at N≈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≈126 would indicate that the r-process at this point is faster than expected, leading to a larger production of the heaviest nuclei.

Production of new neutron-rich isotopes of heavy elements in fragmentation reactions ofU238projectiles at 1AGeV

The production of heavy neutron-rich nuclei has been investigated using cold-fragmentation reactions of $^{238}\mathrm{U}$ projectiles at relativistic energies. The experiment performed at the high-resolving-power magnetic spectrometer Fragment Separator at GSI made it possible to identify $40$ new heavy neutron-rich nuclei: $^{205}\mathrm{Pt}$, $^{207\ensuremath{-}210}\mathrm{Au}$, $^{211\ensuremath{-}216}\mathrm{Hg}$, $^{214\ensuremath{-}217}\mathrm{Tl}$, $^{215\ensuremath{-}220}\mathrm{Pb}$, $^{219\ensuremath{-}224}\mathrm{Bi}$, $^{223\ensuremath{-}227}\mathrm{Po}$, $^{225\ensuremath{-}229}\mathrm{At}$, $^{230,231}\mathrm{Rn}$, and $^{233}\mathrm{Fr}$. The production cross sections of these nuclei were also determined and used to benchmark reaction codes that predict the production of nuclei far from stability.

First approach to half-life measurements around N=126

The present piece of work reviews recent progress on β-decay half-life measurements around the neutron shell N=126. The production of heavy neutron-rich nuclei is discussed, including the present status of the experimental data available for this region of the chart of nuclides. The impact of the theoretical calculations used to model the properties of nuclei involved in the r-process nucleosynthesis is discussed.

New way for the production of heavy neutron-rich nuclei

A new way is found to discover and examine unknown neutron-rich heavy nuclei at the ‘north-east’ part of the nuclear map. This ‘blank spot’ of the nuclear map can be reached neither in fusion–fission reactions nor in fragmentation processes widely used nowadays for the production of new nuclei. The present limits of the upper part of the nuclear map are very close to stability while the unexplored area of heavy neutron-rich nuclides along the neutron closed shell N = 126 (to the east of the stability line) is extremely important for nuclear astrophysics investigations and, in particular, for the understanding of the r-process of astrophysical nucleogenesis. A novel idea is proposed for the production of these nuclei via low-energy multi-nucleon transfer reactions. The estimated yields of neutron-rich nuclei are found to be rather high in such reactions and several tens of new nuclides can be produced, for example, in the near-barrier collision of 136Xe with 208Pb. This finding may spur new studies at heavy-ion facilities and should have significant impact on future experiments.

Production of heavy neutron-rich nuclei “south" of lead

The production of heavy neutron-rich nuclei is investigated using cold-fragmentation reactions. More than 25 new heavy neutron-rich nuclei were produced in the fragmentation of 208Pb projectiles at 1 A GeV impinging a beryllium target. The precise measurement of their production cross sections enables to benchmark the predictive power of different model calculations and make reliable predictions of the production rates expected in future radioactive beam facilities.