Quasifission and fusion-fission in massive nuclei reactions. Comparison of reactions leading to the Z=120 element

TL;DR

This paper analyzes quasifission and fusion-fission processes in reactions leading to element Z=120 using a combined theoretical approach, providing insights into optimal conditions for synthesizing superheavy elements.

Contribution

It introduces a comprehensive theoretical framework combining the dinuclear system concept and statistical models to analyze reaction yields and optimize conditions for superheavy element synthesis.

Findings

Reproduces measured evaporation residue yields accurately.

Decomposes fission fragment contributions into fusion-fission, quasifission, and fast-fission.

Identifies optimal reactions for Z=120 element synthesis with higher evaporation residue yields.

Abstract

The yields of evaporation residues, fusion-fission and quasifission fragments in the $^{48}$Ca+$^{144,154}$Sm and $^{16}$O+$^{186}$W reactions are analyzed in the framework of the combined theoretical method based on the dinuclear system concept and advanced statistical model. The measured yields of evaporation residues for the $^{48}$Ca+$^{154}$Sm reaction can be well reproduced. The measured yields of fission fragments are decomposed into contributions coming from fusion-fission, quasifission, and fast-fission. The decrease in the measured yield of quasifission fragments in $^{48}$Ca+$^{154}$Sm at the large collision energies and the lack of quasifission fragments in the $^{48}$Ca+$^{144}$Sm reaction are explained by the overlap in mass-angle distributions of the quasifission and fusion-fission fragments. The investigation of the optimal conditions for the synthesis of the new element $Z$=120 ($A$=302) show that the $^{54}$Cr+$^{248}$Cm reaction is preferable in comparison with the $^{58}$Fe+$^{244}$Pu and $^{64}$Ni+$^{238}$U reactions because the excitation function of the evaporation residues of the former reaction is some orders of magnitude larger than that for the last two reactions.