First simultaneous measurement of the gamma-ray and neutron emission probabilities in inverse kinematics at a heavy-ion storage ring

TL;DR

This study presents the first simultaneous measurement of gamma-ray and neutron emission probabilities in 208Pb using inverse kinematics at a heavy-ion storage ring, providing data to refine nuclear de-excitation models relevant to astrophysics.

Contribution

It introduces a novel experimental approach to measure emission probabilities simultaneously in inverse kinematics, enabling better constraints on nuclear models.

Findings

Successful simultaneous measurement of gamma-ray and neutron emission probabilities.

Data used to test and refine nuclear de-excitation models.

Enhanced understanding of gamma-ray strength functions and level densities.

Abstract

The probabilities for gamma-ray and particle emission as a function of the excitation energy of a decaying nucleus are valuable observables for constraining the ingredients of the models that describe the de-excitation of nuclei near the particle emission threshold. These models are essential in nuclear astrophysics and applications. In this work, we have for the first time simultaneously measured the gamma-ray and neutron emission probabilities of 208Pb. The measurement was performed in inverse kinematics at the Experimental Storage Ring (ESR) of the GSI/FAIR facility, where a 208Pb beam interacted through the 208Pb(p,p') reaction with a hydrogen gas jet target. Instead of detecting the gamma-rays and neutrons emitted by 208Pb, we detected the heavy beam-like residues produced after gamma and neutron emission. These heavy residues were fully separated by a dipole magnet of the ESR and were detected with outstanding efficiencies. The comparison of the measured probabilities with model calculations has allowed us to test and select different descriptions of the gamma-ray strength function and the nuclear level density available in the literature.