Effects of entrance channels on the deexcitation properties of the same compound nucleus formed by different pairs of collision partners

TL;DR

This study investigates how different entrance channels influence the deexcitation properties of the same $^{220}$Th compound nucleus, revealing that angular momentum distributions significantly affect fission barriers and evaporation residue ratios.

Contribution

It demonstrates that the entrance channel's mass and charge asymmetry impact the angular momentum distribution and deexcitation pathways of the compound nucleus.

Findings

Effective fission barrier is sensitive to entrance channel and angular momentum.

Evaporation residue ratios depend on entrance channel asymmetry.

Deexcitation processes are influenced by initial collision conditions.

Abstract

The properties of deexcitation of the same $^{220}$Th compound nucleus (CN) formed by different mass (charge) asymmetric reactions are investigated. It is demonstrated that the effective fission barrier $<B_{\rm fis}>$ value being a function of the excitation energy $E^*_{\rm CN}$ is strongly sensitive to the various orbital angular momentum $L=\ell\hbar$ distributions of CN formed with the same excitation energy $E^*_{CN}$ by the very different entrance channels $^{16}$O+$^{204}$Pb, $^{40}$Ar+$^{180}$Hf, $^{82}$Se+$^{138}$Ba and $^{96}$Zr+$^{124}$Sn. Consequently, the competition between the fission and evaporation of light particles (neutron, proton, and $\alpha$-particle) processes along the deexcitation cascade of CN depends on the orbital angular momentum distribution of CN. Therefore, the ratio between the evaporation residue cross sections obtained after emission of neutral and charged particles and neutrons only for the same CN with a given excitation energy $E^*_{CN}$ is sensitive to the mass (charge) asymmetry of reactants in the entrance channel.