Concentrated valence nucleons transfer in heavy-ion collisions: implications for questing the stable superheavy elements

Abstract

The multinucleon transfer process is regarded as a promising pathway for producing the stable superheavy elements. However, the underlying mechanism, especially the possible transfer channels for sailing to the ``island of stability'' are poorly known. In this work, the time-dependent Hartree-Fock theory is used to investigate the collision dynamics of $^{136}$Xe, $^{198}$Pt, $^{238}$U + $^{238}$U reactions. A novel reaction channel of the concentrated valence nucleons (CVN) transferring is found in the collisions heading on the tips of $^{238}$U. These nucleons are transferred with relatively short relaxation time and break the symmetry of nucleon exchange in the early reaction stage. In consequence, the mass equilibrium with relaxation time is deviated from the systematic behavior based on the macroscopic-microscopic potential energy surface. The CVN transfer channel shows promising prospect for producing neutron-rich superheavy nuclei. In this case, we also investigated the angular distributions of products from the CVN transfer channel in the reaction $^{238}$U + $^{238}$U with Tip-Side configuration, and the optimal detection angles are predicted.

Figures (7)

• Figure 1: The reaction contact time (a), the number of the net nucleon transferring from the $^{238}$U to the $^{136}$Xe (b) and $^{198}$Pt (c), as functions of the reduced incident center-of-mass energy with impact parameter $b$ = 0 fm. The solid and dotted line represent reactions in the $x$- and $y$-direction, respectively.
• Figure 2: The net nucleon transfer number from the target to the projectile (a) and the contact time (b) as functions of impact parameter in the reaction of $^{136}$Xe+$^{238}$U at $E_{\rm c.m.}$ = 636 MeV. Solid, dotted, and dashed line denote the results obtained by TDHF with the $x$-, $y$-, and $z$-direction, respectively.
• Figure 3: Time evolution of the normalized two dimensional density distributions of twenty valence nucleons of $^{238}$U for $x$- and $y$-direction reactions of $^{136}$Xe+$^{238}$U at $E_{\rm c.m.}$ = 636 MeV, $b$ = 0 fm. The dashed line of isodensity corresponds to $\rho=0.03$ fm$^{-3}$.
• Figure 4: Time evolution (a logarithmic scale is used) for nucleon transfer number contributed from all nucleons (a) and 20 valence nucleons (c) in the reaction of $^{136}$Xe+$^{238}$U at $E_{\rm c.m.}$ = 636 MeV, $b$ = 0 fm. The blue and orange lines represent the $x$- and $y$-direction, respectively. Solid lines indicate nucleon transfer from $^{238}$U to $^{136}$Xe, while dashed lines denote the inverse transfer. The shaded area illustrates the net transfer number. The time region from 160 fm/$c$ to 200 fm/$c$ is enlarged in (b).
• Figure 5: The angular distributions of primary fragment cross sections for each channel of net transfer particle number in the reaction of $^{238}$U + $^{238}$U at $E_{\rm c.m.}$ = 800 MeV.