# Approaching the Gamow window with stored ions: Direct measurement of $^{124}$Xe(p,$\gamma$) in the ESR storage ring

## TL;DR

This paper presents the first direct measurement of low-energy proton-capture cross sections of $^{124}$Xe using a heavy ion storage ring, providing critical data for astrophysical models of explosive stellar environments.

## Contribution

It introduces a novel experimental approach to measure nuclear reaction rates at energies relevant to astrophysics using stored ions in a heavy ion storage ring.

## Key findings

- Good agreement with theoretical predictions of proton width at low energies.
- Measured cross sections are on the high energy tail of the Gamow window.
- Method enables investigation of nuclear reactions on rare ion beams at low energies.

## Abstract

We report the first measurement of low-energy proton-capture cross sections of $^{124}$Xe in a heavy ion storage ring. $^{124}$Xe$^{54+}$ ions of five different beam energies between 5.5 AMeV and 8 AMeV were stored to collide with a windowless hydrogen target. The $^{125}$Cs reaction products were directly detected. The interaction energies are located on the high energy tail of the Gamow window for hot, explosive scenarios such as supernovae and X-ray binaries. The results serve as an important test of predicted astrophysical reaction rates in this mass range. Good agreement in the prediction of the astrophysically important proton width at low energy is found, with only a 30% difference between measurement and theory. Larger deviations are found above the neutron emission threshold, where also neutron- and ${\gamma}$-widths significantly impact the cross sections. The newly established experimental method is a very powerful tool to investigate nuclear reactions on rare ion beams at low center-of-mass energies.