Evidence for a Novel Reaction Mechanism of a Prompt Shock-Induced Fission Following the Fusion of 78Kr and 40Ca Nuclei at E/A =10 MeV

TL;DR

This paper presents evidence for a novel, intermediate reaction mechanism in nuclear fission following a specific fusion process at 10 MeV per nucleon, revealing new insights into nuclear collision dynamics.

Contribution

It uncovers a previously unknown reaction mechanism that combines features of fusion and dynamic fission, distinct from established models like fast fission or quasi-fission.

Findings

Identification of a new reaction mechanism between fusion and fission.

Observation of broad mass spectrum centered around symmetric fission.

Fragments show higher velocities along the fission axis and no intrinsic spin.

Abstract

An analysis of experimental data from the inverse-kinematics ISODEC experiment on 78Kr+40Ca reaction at a bombarding energy of 10 AMeV has revealed signatures of a hitherto unknown reaction mechanism, intermediate between the classical damped binary collisions and fusion-fission, but also substantially different from what is being termed in the literature as fast fission or quasi fission. These signatures point to a scenario where the system fuses transiently while virtually equilibrating mass asymmetry and energy and, yet, keeping part of the energy stored in a collective shock-imparted and, possibly, angular momentum bearing form of excitation. Subsequently the system fissions dynamically along the collision or shock axis with the emerging fragments featuring a broad mass spectrum centered around symmetric fission, relative velocities somewhat higher along the fission axis than in transverse direction, and virtually no intrinsic spin. The class of massasymmetric fission events shows a distinct preference for the more massive fragments to proceed along the beam direction, a characteristic reminiscent of that reported earlier for dynamic fragmentation of projectile-like fragments alone and pointing to the memory of the initial mass and velocity distribution.