Small cross section of the synthesis of darmstadtium in the $^{48}$Ca+$^{232}$Th reaction

TL;DR

This paper analyzes the extremely small cross section of evaporation residues in the $^{48}$Ca+$^{232}$Th reaction using the dinuclear system model, explaining the effects of quasifission and shell effects on the yield.

Contribution

It provides a theoretical analysis of the small cross section in superheavy element synthesis, incorporating dynamical modeling and shell effects, aligning with experimental data.

Findings

Quasifission significantly reduces residue yield.

Shell effects lower the fission barrier for certain isotopes.

Theoretical results agree with experimental measurements.

Abstract

The smallness of the cross section of evaporation residues formed in the hot fusion reaction $^{48}$Ca+$^{232}$Th is analyzed by the dinuclear system model (DNS). The capture probability has been calculated by solving the dynamical equations of motion for the relative distance between the centers-of-mass of the DNS nuclei. Fusion of nuclei is considered as evolution of the DNS to a stable compound nucleus. The fusion probability has a bell-like shape and quasifission is one of reasons causing smallness of the yield of the evaporation residues products. Another reason is the decrease of the fission barrier for the isotopes $^{275-285}$Dm related with the shell effects in the neutron structure. The agreement of the theoretical results obtained for the yield of the evaporation residues with the experimental data measured in the Factory of superheavy elements of Joint Institute for Nuclear Research is well.