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

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.

arXiv comment8 pages, 3 figures, submitted to Physical Review C, fixed a typo in a figure caption and some improvements for clarity in Figure 2, added information on rate implications for alpha-particle radiative capture on Ne-22

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Cited by in corpus (9)

• Electric and magnetic dipole modes in high-resolution inelastic proton scattering at $0^{\circ }$
• Re-evaluation of the ${}^{22}$Ne($\alpha ,\gamma$)${}^{26}$Mg and ${}^{22}$Ne($\alpha ,n$)${}^{25}$Mg reaction rates
• Constraining the ${}^{22}$Ne($\alpha$,$\gamma$)${}^{26}$Mg and ${}^{22}$Ne($\alpha$,n)${}^{25}$Mg reaction rates using sub-Coulomb $\alpha$-transfer reactions
• Decay properties of ${}^{22}\mathrm{Ne}+\alpha$ resonances and their impact on $s$-process nucleosynthesis
• A high-resolution study of levels in the astrophysically important nucleus ${}^{26}$Mg and resulting updated level assignments
• Study of (${}^6$Li, $d$) and (${}^6$Li, $t$) reactions on ${}^{22}$Ne and implications for $s$-process nucleosynthesis
• Isoscalar monopole and dipole transitions in ${}^{24}$Mg, ${}^{26}$Mg and ${}^{28}$Si
• The ${}^{22}$Ne($\alpha$,n)${}^{25}$Mg reaction -- state of the art, astrophysics, and perspectives
• Impact of the latest 22Ne+α reaction rates on nucleosynthesis in massive stars and galactic chemical evolution