# Re-examining the $^{26}$Mg($\alpha,\alpha^\prime$)$^{26}$Mg reaction - probing astrophysically important states in $^{26}$Mg

## TL;DR

This study re-examines the excited states of $^{26}$Mg relevant to astrophysical neutron production, using inelastic alpha scattering to identify new states and challenge previous spin-parity assignments, highlighting the need for higher resolution experiments.

## Contribution

The paper provides new experimental data on $^{26}$Mg states via inelastic alpha scattering, including the discovery of a new $0^+$ state and revised spin-parity assignments, improving understanding of nuclear levels affecting the $s$-process.

## Key findings

- Discovery of a new $0^+$ state in $^{26}$Mg.
- Discrepancies in $J^ ext{pi}$ assignments compared to previous experiments.
- High level density complicates definitive state assignments.

## Abstract

Background: The $^{22}$Ne($\alpha,n$)$^{25}$Mg reaction is one of the neutron sources for the $s$-process in massive stars. The properties of levels in $^{26}$Mg above the $\alpha$-particle threshold control the strengths of the $^{22}$Ne($\alpha,n$)$^{25}$Mg and $^{22}$Ne($\alpha,\gamma$)$^{26}$Mg reactions. The strengths of these reactions as functions of temperature are one of the major uncertainties in the $s$-process. Methods: Inelastically scattered $\alpha$ particles from a $^{26}$Mg target were momentum-analysed in the K600 magnetic spectrometer at iThemba LABS, South Africa. The differential cross sections of states were deduced from the focal-plane trajectory of the scattered $\alpha$ particles. Based on the differential cross sections, spin and parity assignments to states are made. Results: A new $0^+$ state was observed in addition to a number of other states, some of which can be associated with states observed in other experiments. Some of the deduced $J^\pi$ values of the states observed in the present study show discrepancies with those assigned in an experiment performed at RCNP Osaka. Conclusion: The high level density at this excitation energy in $^{26}$Mg makes assigning $J^\pi$ values to observed states difficult. Further experimental investigations with superior experimental energy resolution are required to clarify the number of levels in $^{26}$Mg, especially between the $\alpha$-particle threshold at 10.615 MeV and the neutron threshold at 11.319 MeV.