Background: Heavy-ion fusion reactions play a crucial role in various aspects of nuclear physics and astrophysics. The nuclear interaction potential and hence the fusion barrier formed between the interacting nuclei are the keys to understanding the complex fusion process dynamics. Thus, a theoretical investigation of fusion barrier characteristics which includes the relativistic effects is of paramount significance.

Purpose: This work intends to explore the fusion barrier characteristics of different target-projectile combinations within the relativistic mean-field (RMF) formalism. The M3Y nucleon-nucleon (NN) potential is compared with the relativistic R3Y and density-dependent R3Y (DDR3Y) NN potentials within the double folding approach. A systematic study is carried out to study the effect of different RMF density distributions and effective NN interactions on the fusion and/or capture cross section of 24 target-projectile combinations leading to heavy and superheavy nuclei (SHN).

Methods: The density distributions of interacting nuclei and the microscopic R3Y NN interaction are obtained from the RMF formalism for nonlinear NL1, NL3, and TM1 parameter sets and the relativistic Hartree-Bogoliubov (RHB) approach for the DDME2 parameter set. The medium-independent relativistic R3Y, the density-dependent DDR3Y, and widely adopted M3Y NN potentials are used to obtain the nuclear interaction potential within the double folding approach. The densities for the projectiles and targets are obtained from the relativistic mean-field approaches. The fusion and/or capture cross section for the different reaction systems is calculated using the well-known $\ell$-summed Wong model.

Results: The barrier height and position of 24 heavy-ion reaction systems are obtained for different nuclear density distributions and effective NN interaction potentials. We have considered the lighter mass projectile and heavier mass target combinations for synthesizing exotic drip-line nuclei, including the superheavy nuclei (SHN). These reactions include the even-even ${}^{48}\mathrm{Ca}+{}^{154}\mathrm{Sm}$, ${}^{48}\mathrm{Ca}+{}^{238}\mathrm{U}$, ${}^{48}\mathrm{Ca}+{}^{248}\mathrm{Cm}$, and ${}^{26}\mathrm{Mg}+{}^{248}\mathrm{Cm}$; even-odd ${}^{46}\mathrm{K}+{}^{181}\mathrm{Ta}$; odd-odd ${}^{31}\mathrm{Al}+{}^{197}\mathrm{Au}$ and ${}^{39}\mathrm{K}+{}^{181}\mathrm{Ta}$; and also 17 other systems for the synthesis of SHN $Z=120$. The comparison of fusion and/or capture cross section obtained from the $\ell$-summed Wong model is made with the available experimental data.

Conclusions: The phenomenological M3Y NN potential is observed to give higher barrier heights than the relativistic R3Y NN potential for all the reaction systems. The comparison of results obtained from different relativistic parameter sets shows that the densities from NL1 and TM1 parameter sets give the lowest and highest barrier heights for all the systems under study. The density dependent DDR3Y NN potential is obtained within the relativistic Hartree-Bogoliubov approach for the DDME2 parameter set. We observed higher barrier heights and lower cross sections for the DDR3Y NN potential as compared to density-independent R3Y NN potentials obtained for considered nonlinear NL1, NL3, and TM1 parameter sets. According to the present analysis, it is concluded that the NL1 and NL3 parameter sets provide comparatively better overlap with the experimental fusion and/or capture cross section than the TM1 and DDME2 parameter sets.

• Received 19 October 2021
• Revised 14 March 2022
• Accepted 9 May 2022

DOI:https://doi.org/10.1103/PhysRevC.105.054613