Neck Rupture and Scission Neutrons in Nuclear Fission

TL;DR

This paper provides the first fully microscopic analysis of the nuclear fission scission process, including neutron emission spectra and spatial distribution, filling a long-standing gap in understanding this highly non-equilibrium stage.

Contribution

It introduces a fully quantum many-body framework to characterize the fission scission mechanism and neutron emission, which was previously lacking.

Findings

Microscopic spectrum of scission neutrons

Spatial distribution of emitted neutrons

Upper limit estimates for charged particle emission

Abstract

Just before a nucleus fissions a neck is formed between the emerging fission fragments. It is widely accepted that this neck undergoes a rather violent rupture, despite no direct experimental evidence, and only a few contentious theoretical treatments of this fission stage were ever performed in the more than eight decades since nuclear fission was experimentally observed by Hahn and Strassmann and described by Meitner and Frisch in 1939. In the same year, Bohr and Wheeler conjectured that the fission of the nuclear liquid drop would likely be accompanied by the rapid formation of tiny droplets, later identified with either scission neutrons or other ternary fission fragments, a process which has not yet been discussed in a fully quantum many-body framework. The main difficulty in addressing both of these stages of nuclear fission is both are highly non-equilibrium processes. Here we will present the first fully microscopic characterization of the scission mechanism, along with the spectrum and the spatial distribution of scission neutrons, and some upper limit estimates for the emission of charged particles.