Optimum orientation of compact and elongated hexadecapole deformed actinide targets: Application to synthesizing superheavy nuclei

Background: The quadrupole (beta 2 +/-) deformed targets in the actinide region are found to be of great relevance in the production of superheavy nuclei (SHN), in both the hot and cold fusion mechanisms. Recently, the application of elongated or cold and compact or hot configurations of pear-shape octupole (up to beta 3 +/-) deformed nuclei was found to play significant role in the fusion-fission dynamics of heavy-ion induced reactions, in the low energy regime.Purpose: To understand the relevance of higher-order deformed (up to beta 4 +/-) actinides and their compact and elongated nuclear fusion configurations in the production cross section of SHN, we have obtained the optimum orientations (theta opt) in reference to the above mentioned configurations of beta 4-deformed targets. For this, a variety of projectile-target combinations-spherical (36S, 40,48Ca) and beta 2 +/--deformed (30Si, 34S) nuclei as incident beams and beta 4-deformed (with different signs +/- and magnitudes) actinides (approximate to 1400 isotopes) as targets-are taken into consideration. Later, the application of theta hot/cold opt (beta 2 +/-beta 3 +/-beta 4 +/-) was done to analyze the fragmentation structure of 286Cn*.Methods: On the basis of the proximity theorem, the optimum orientations (theta opt) defining the compact and elongated configurations of deformed nuclei are obtained at the maximum and minimum barrier height, respectively. Further, the obtained theta opt and static deformations (up to beta 4 +/-) for around 1400 isotopes of actinides are utilized in the calculations of capture cross section sigma cap(Ec.m.) using the extended -summed Wong model at energies lying across the Coulomb barrier. Also, to study the fragmentation structure of 286Cn* SHN, the collective clusterization approach of quantum mechanical fragmentation theory has been adopted. Results: For a large variety of projectile-target combinations, leading to SHN, the incorporation of higher order deformation (up to beta 4 +/-) shows a significant influence on theta hot/cold opt with the effect of +/- signs and different magnitudes of beta 4 +/- deformation. Also, with the incorporation of deformations up to beta 4 +/- and corresponding theta opt, the sigma cap(Ec.m.) improves and is in better agreement with the available experimental data of 238U-based reactions, across the barrier energies. Also, in the decay channel, the beta 4-deformed fragments, i.e., 143Ba + 143Ba, are found to minimize the fragmentation potential, as compared to the beta 2 or beta 3 deformed fragments.Conclusion: The present study concludes that the optimized configurations of higher-order deformed actinides up to beta 4 participate relatively better than the optimized configurations of beta 2 and beta 3 deformed nuclei in the formation as well as exit channel of superheavy nuclei.

Automated summary

This study investigates the influence of higher-order deformed actinides and their fusion configurations on the production cross section and fragmentation structure of superheavy nuclei (SHN). The results show that higher-order deformations have a significant impact on the fusion configurations and improve the agreement with experimental data.