Fusion Hindrance in the Heavy Ion Reactions -- Border Between the Normal and Hindered Fusions

TL;DR

This paper investigates fusion hindrance in heavy ion reactions using a two-center liquid drop model, classifying reactions based on the presence of hindrance and analyzing how these depend on mass asymmetry.

Contribution

It introduces a systematic classification of fusion hindrance types in heavy ion collisions and analyzes their dependence on mass asymmetry and reaction parameters.

Findings

Reactions without radial fusion hindrance are fewer than those without neck hindrance.

Fewer reactions are hindered at larger mass asymmetry parameters.

If a reaction with a certain critical asymmetry is unhindered, others with higher asymmetry are also unhindered.

Abstract

The fusion hindrance in heavy ion collisions is studied in the framework of the two-center liquid drop model. It appears that the neck and the radial degrees of freedom might both be hampered by an inner potential barrier on their path between the contact configuration to the compound nucleus. Heavy ion reactions with and without the two kinds of fusion hindrance are classified through systematic calculations. It is found that the number of reactions without radial fusion hindrance is much smaller than that without neck fusion hindrance, and for both kinds of fusion hindrance the number of reactions without fusion hindrance at small mass-asymmetry parameter $\alpha$ is smaller than that at large $\alpha$. In the formation of a given compound nucleus, if a reaction with $\alpha_c$ is not hindered, then other reactions with $\alpha > \alpha_c$ are also not hindered as it is well known experimentally.