The measurements of complete fusion cross sections for ${}^6\mathrm{Li}+{}^{96}\mathrm{Zr}$ have been performed at energies around the Coulomb barrier by the online $\gamma$-ray method. The complete fusion cross sections at above-barrier energies were found to be suppressed by $\sim 25\%$. A comparison of the systematics of complete fusion suppression with the existing data for ${}^6\mathrm{Li}$+ heavy targets with the present results shows that the systematics of the suppression factor observed for ${}^6\mathrm{Li}$-induced fusion in the heavy mass region may not be consistent in lighter target mass region.

The $\alpha$ preformation factor and the penetration probability are carefully analyzed for heavy and superheavy even-even nuclei. The penetration probability of an $\alpha$ cluster in the parent nucleus is calculated within the WKB approximation, whereas the nuclear potential between an $\alpha$ cluster and the daughter nucleus is obtained in the frame of a double-folding model with a density-dependent nucleon-nucleon interaction, in which the zero-range exchange term is supplemented. The $\alpha$ preformation factors in different shell regions are compared. It is shown that shell effects play an important role in $\alpha$ preformation. The preformation factor can supply information on the nuclear structure, and the penetration probability mainly determines the $\alpha$-decay half-life. The results indicate that the deformed-subshell region at $N=162$ is different from that at $N=152$, and $Z=114$ and $N=184$ may lie in the closed-shell region.

Measurements of complete and incomplete fusion cross sections for ${}^6\mathrm{Li}+{}^{154}\mathrm{Sm}$ have been performed at energies above the Coulomb barrier by the online $\gamma$-ray method, to investigate the effect of breakup and inelastic couplings on the complete fusion (CF) of this weakly bound system. We show that inelastic excitation couplings have non-negligible effects, when compared with the breakup effect, for deformed nuclei at energies very close to the Coulomb barrier. The average CF suppression corresponding to dynamic breakup effects was found to be around 35%. The total fusion cross section is not affected by the breakup coupling. A comparison between the ${}^6\mathrm{Li}$-induced CF suppression for three different samarium isotopes shows that the breakup effect is larger for the more spherical isotope.

The experimental data of fusion cross sections for the different projectile and target nuclei systems are systematically analyzed. In order to explore the positive $Q$-value neutron transfer (PQNT) effect we systematically analyze their fusion functions F($x$) as a function of $x$, which reduces the barrier height, radius, and curvature of fusion systems. From the comparison of F($x$)s among them, it is found that after neutron transfer when the deformation of interacting nuclei increases largely, the enhancement of fusion cross sections can be observed at energies below the Coulomb barrier due to the PQNT effect. However, even if the fusion systems show the PQNT values, the fusion cross sections are almost the same due to the small deformation of interaction nuclei after neutron transfer. Many experiments need to be systematically done for this research. DOI: http://dx.doi.org/10.1103/PhysRevC.89.054602 ©2014 American Physical Society