Impact of octupole correlation on the inverse quasifission in ${}^{160}\text{Gd}+{}^{186}\text{W}$ collisions

Abstract

Multinucleon transfer (MNT) reactions offer a promising pathway to synthesize neutron-rich heavy nuclei, but the mechanism of inverse quasifission, as a key reaction channel of MNT, still remains not well understood. We employ time-dependent Hartree-Fock theory to investigate the reaction mechanism, especially the role of the octupole deformed shell in the MNT reaction of ${}^{160}\text{Gd}+{}^{186}\text{W}$. The results show that inverse quasifission occurs when the deformed projectile and target collide in near tip-tip and tip-side orientations, which favors production of neutron-rich transtarget nuclei. Interestingly, the distributions and single-particle spectra of primary products reveal that the $N=88$ octupole deformed shell in light fragments dominates inverse quasifission instead of the spherical shells of $^{208}\text{Pb}$ at a center-of-mass energy of $502.6~\text{MeV}$, thus explaining the experimental observation that the yields of the transtarget products are enhanced in the Au region. Further exploration finds that quantum shell effects in inverse quasifission exhibit energy dependence. These results demonstrate that the octupole deformed shell plays a crucial role in the inverse quasifission dynamics, significantly advancing the understanding of the MNT reaction mechanism.

Figures (6)

• Figure 1: Time evolution of isodensity surfaces at $0.03~\text{fm}^{-3}$ for a typical inverse quasifission process in the tip-side ($\theta_{\text{P}}=0^\circ$ and $\theta_{\text{T}}=90^\circ$) reaction of ${}^{160}\text{Gd}+{}^{186}\text{W}$ at $E_{\text{c.m.}}=502.6~\text{MeV}$ and $b=2~\text{fm}$. The reaction times, initial reactants, and resulting fragments are labeled.
• Figure 2: Transferred nucleon numbers in central collisions of ${}^{160}\text{Gd}+{}^{186}\text{W}$ as a function of initial orientations of projectile at $E_\text{c.m.}=502.6$ MeV. The upper and lower panels are for the tip and side orientations of the target ($\theta_\text{T}=0^\circ$ and $90^\circ$), respectively. The density profiles for various orientations are also shown at the top of each panel.
• Figure 3: Transferred proton (upper panel) and neutron (lower panel) numbers as a function of the impact parameter for four extreme initial orientations: tip-tip, tip-side, side-tip, side-side in the reaction ${}^{160}\text{Gd}+{}^{186}\text{W}$ at $E_\text{c.m.}=502.6$ MeV. In the lower panel, contact time (right axis) is displayed for tip-tip (circles) and tip-side (triangles) orientations.
• Figure 4: Neutron-proton distributions of primary fragments in the tip-side collision of ${}^{160}\text{Gd}+{}^{186}\text{W}$ at $E_\text{c.m.} = 502.6$ MeV. The projectile and target nuclei are indicated by the black solid squares. The empty squares represent the nuclei discovered until the year 2021 Thoennessen_web. The position of the $N=88$ shell is indicated by the gray rectangle.
• Figure 5: Single-particle energy levels of the neutron (upper panel) and proton (lower panel) for $^{144,~146,~148}\text{Ce}$ and $^{146,~148,~150}\text{Nd}$. The dashed line denotes the Fermi level. Shell gaps at $N = 84,~88$ and $Z=52,~56$ are labeled.