Probing pre-formed alpha particles in the ground state of nuclei

TL;DR

This paper investigates alpha particle emission in calcium-40 nuclear reactions, revealing that alpha particles can be emitted with specific angular distributions due to pre-formed alpha clusters, and presents a time-dependent theory to model this process.

Contribution

It introduces a new understanding of alpha particle emission as resulting from pre-formed alpha clusters in nuclei, supported by a time-dependent theoretical model.

Findings

Alpha particles are emitted with specific angular distributions.

A time-dependent model qualitatively reproduces observed distributions.

Alpha cluster properties can be studied through this emission mechanism.

Abstract

In this Letter, we report on alpha particle emission through the nuclear break-up in the reaction 40Ca on a 40Ca target at 50A MeV. It is observed that, similarly to nucleons, alpha particles can be emitted to the continuum with very specific angular distribution during the reaction. The alpha particle properties can be understood as resulting from an alpha cluster in the daughter nucleus that is perturbed by the short range nuclear attraction of the collision partner and emitted. A time-dependent theory that describe the alpha particle wave-function evolution is able to reproduce qualitatively the observed angular distribution. This mechanism offers new possibilities to study alpha particle properties in the nuclear medium.