Angular anisotropy of the fusion-fission and quasifission fragments

TL;DR

This paper investigates the angular anisotropy in fusion-fission and quasifission fragments across different nuclear reactions, revealing how quasifission influences anisotropy deviations from statistical models and varies with energy and system properties.

Contribution

It introduces a detailed analysis of angular momentum distributions and orientation angles to explain anisotropy deviations, highlighting the role of quasifission in different reactions.

Findings

Quasifission significantly affects angular anisotropy in certain reactions.

Anisotropy enhancement at low energies is linked to low-temperature quasifission.

Deviations from statistical models are connected to quasifission contributions.

Abstract

The anisotropy in the angular distribution of the fusion-fission and quasifission fragments for the $^{16}$O+$^{238}$U, $^{19}$F+$^{208}$Pb and $^{32}$S+$^{208}$Pb reactions is studied by analyzing the angular momentum distributions of the dinuclear system and compound nucleus which are formed after capture and complete fusion, respectively. The orientation angles of axial symmetry axes of colliding nuclei to the beam direction are taken into account for the calculation of the variance of the projection of the total spin onto the fission axis. It is shown that the deviation of the experimental angular anisotropy from the statistical model picture is connected with the contribution of the quasifission fragments which is dominant in the $^{32}$S+$^{208}$Pb reaction. Enhancement of anisotropy at low energies in the $^{16}$O+$^{238}$U reaction is connected with quasifission of the dinuclear system having low temperature and effective moment of inertia.