Effect of isospin diffusion on the production of neutron-rich nuclei in multinucleon transfer reactions

The isospin dissipation dynamics in multinucleon transfer reactions has been investigated within the dinuclear system model. Production cross sections of neutron-rich isotopes around projectile-like and target-like fragments are estimated in collisions of ${}^{58,64}\mathrm{Ni}+{}^{208}\mathrm{Pb}$ and ${}^{78,86,91}\mathrm{Kr}+{}^{198}\mathrm{Pt}$ near Coulomb barrier energies. The isospin diffusion in the nucleon transfer process is coupled to the dissipation of relative motion energy and angular momentum of colliding system. The available data of projectile-like fragments via multinucleon transfer reactions are nicely reproduced. It is found that the light projectile-like fragments are produced in the neutron-rich region because of the isospin equilibrium in two colliding nuclei. However, the heavy target-like fragments tend to be formed on the neutron-poor side above the $\beta$-stability line. The neutron-rich projectiles move the maximal yields of heavy nuclei to the neutron-rich domain and are available for producing the heavy exotic isotopes, in particular around the neutron shell closure of $N=126$.

Figure 1

The potential energy surface in the reaction of ${}^{58}\mathrm{Ni}+{}^{208}\mathrm{Pb}$ as functions of the protons and neutrons of (a) the projectile-like and (b) target-like fragments.

Figure 2

Projectile-like fragment distributions in the transfer reaction of ${}^{58}\mathrm{Ni}+{}^{208}\mathrm{Pb}$ at the reduced energy of $E_{\text{c.m.}}/V_C=1.07$ and compared with the available data [44].

Figure 3

The survived target-like fragments in the reactions of ${}^{58}\mathrm{Ni}+{}^{208}\mathrm{Pb}$ and ${}^{64}\mathrm{Ni}+{}^{208}\mathrm{Pb}$ at the reduced energies of 1.07 and 1.14, respectively.

Figure 4

The charge and mass distributions of fragments produced in the MNT reaction of ${}^{64}\mathrm{Ni}+{}^{208}\mathrm{Pb}$ at the reduced energies of 1.05, 1.14, and 1.2, respectively. The available data of the mass spectra in ${}^{64}\mathrm{Ni}+{}^{208}\mathrm{Pb}$ collisions at the energy of 1.14 are shown for comparison [45].

Figure 5

Isotopic distributions of Lu, Hf, Ta, W, Re, Os, Ir, and Pt in the MNT reactions with ${}^{78,86,91}\mathrm{Kr}$ bombarding ${}^{198}\mathrm{Pt}$ at the reduced energy of 1.14. The open symbols denote the new isotopes in the nuclear chart.

Figure 6

Isotonic distributions of $N=126$ in the MNT reactions of ${}^{78,86,91}\mathrm{Kr}+{}^{198}\mathrm{Pt}$.