Quasifission and difference in formation of evaporation residues in the $^{16}$O+$^{184}$W and $^{19}$F+$^{181}$Ta reactions

TL;DR

This study theoretically compares the formation of evaporation residues in $^{16}$O+$^{184}$W and $^{19}$F+$^{181}$Ta reactions, explaining differences through quasifission contributions and capture cross sections to understand yield variations.

Contribution

It provides a detailed theoretical analysis of how quasifission affects evaporation residue formation in two similar reactions leading to $^{200}$Pb, highlighting the role of capture cross sections and hindrance factors.

Findings

Higher capture cross section in $^{16}$O+$^{184}$W leads to more evaporation residues.

Increased quasifission in $^{19}$F+$^{181}$Ta reduces residue formation at high energies.

Similar angular momentum ranges for compound nuclei in both reactions.

Abstract

The excitation functions of capture, complete fusion, and evaporation residue formation in the $^{16}$O+$^{184}$W and $^{19}$F+$^{181}$Ta reactions leading to the same $^{200}$Pb compound nucleus has been studied theoretically to explain the experimental data showing more intense yield of evaporation residue in the former reaction in comparison with that in the latter reaction. The observed difference is explained by large capture cross section in the former and by increase of the quasifission contribution to the yield of fission-like fragments in the $^{19}$F+$^{181}$Ta reaction at large excitation energies. The probability of compound nucleus formation in the $^{16}$O+$^{184}$W reaction is larger but compound nuclei formed in both reactions have similar angular momentum ranges at the same excitation energy. The observed decrease of evaporation residue cross section normalized to the fusion cross section in the $^{19}$F+$^{181}$Ta reaction in comparison with the one in the $^{16}$O+$^{184}$W reaction at high excitation energies is explained by the increase of hindrance in the formation of compound nucleus connected with more quick increase of the quasifission contribution in the $^{19}$F induced reaction. The spin distributions of the evaporation residue cross sections for the two reactions are also presented.