Ternary fission with the emission of long-range $\alpha$ particles in fission of the heaviest nuclei

TL;DR

This paper reviews and analyzes experimental data on long-range alpha particle emission in ternary fission of heavy nuclei, extending understanding to superheavy elements with high fissility parameters.

Contribution

It introduces a semi-empirical model for LRA emission probability, expanding analysis to neutron-deficient and superheavy nuclei beyond previous fissility ranges.

Findings

LRA emission probabilities are significant in superheavy nuclei.

The semi-empirical model aligns well with experimental data.

Probability increases with fissility parameter in the studied range.

Abstract

The most probable outcome of the ternary fission is the emission of two heavy fragments and one light-charged particle. In about 90\%, these are $\alpha$ particles, which often referred to as the long-range alpha (LRA). Such decay has been extensively studied over decades in various heavy fissioning systems. The probability of such a process has been found to be about (2-4)$\times 10^{-3}$ relative to binary fission. The experimental data showed an increasing trend in the probability of such a process with an increase in fissility parameter within the range of 35 - 39. In the last decades, a region of the heaviest nuclei has been substantially expanded in both proton and neutron numbers. This includes neutron-deficient heavy and superheavy nuclei with fissility parameters, which are significantly exceeding the aforementioned range. In the present work, the currently available experimental data on the probability of the LRA emission, which is a representative of ternary fission, are discussed. The probabilities of LRA emission were calculated within the various empirical approaches, including the presently suggested semi-empirical expression. The latter one was derived on the basis of the $\alpha$-decay property of the fissioning nucleus. The results of all approaches discussed show that the probabilities of LRA emission are substantial (up to a percentage) in the fission of neutron-deficient heavy and superheavy nuclei.