Probing astrophysically important states in ${}^{26}$Mg nucleus to study neutron sources for the $s$-Process

Abstract

The ${}^{22}$Ne($\alpha$,n)${}^{25}$Mg reaction is the dominant neutron source for the slow neutron capture process ($s$-process) in massive stars and contributes, together with the ${}^{13}$C($\alpha$,n)${}^{16}$O, to the production of neutrons for the $s$-process in Asymptotic Giant Branch (AGB) stars. However, the reaction is endothermic and competes directly with the ${}^{22}$Ne($\alpha ,\gamma {)}^{26}$Mg radiative capture. The uncertainties for both reactions are large owing to the uncertainty in the level structure of ${}^{26}$Mg near the alpha and neutron separation energies. These uncertainties are affecting the s-process nucleosynthesis calculations in theoretical stellar models. Indirect studies in the past have been successful in determining the energies, $\gamma$-ray and neutron widths of the ${}^{26}$Mg states in the energy region of interest. But, the high Coulomb barrier hinders a direct measurement of the resonance strengths, which are determined by the $\alpha$-widths for these states. The goal of the present experiments is to identify the critical resonance states and to precisely measure the $\alpha$-widths by $\alpha$ transfer techniques . Hence, the $\alpha$-inelastic scattering and $\alpha$-transfer measurements were performed on a solid ${}^{26}$Mg target and a ${}^{22}$Ne gas target, respectively, using the Grand Raiden Spectrometer at RCNP, Osaka, Japan. Six levels (E${}_x$ = 10717 keV , 10822 keV, 10951 keV, 11085 keV, 11167 keV and 11317 keV) have been observed above the $\alpha$-threshold in the region of interest (10.61 - 11.32 MeV). The rates are dominated in both reaction channels by the resonance contributions of the states at E${}_x$ = 10951, 11167 and 11317 keV. The E${}_x$ =11167 keV has the most appreciable impact on the ($\alpha ,\gamma$) rate and therefore plays an important role for the prediction of the neutron production in s-process environments.

References in corpus (11)

• The Dawes Review 2: Nucleosynthesis and stellar yields of low and intermediate-mass single stars
• Galactic Chemical Evolution and solar s-process abundances: dependence on the 13C-pocket structure
• The s process in massive stars at low metallicity. Effect of primary N14 from fast rotating stars
• Galactic evolution of rapid neutron capture process abundances: the inhomogeneous approach
• Galactic r-process enrichment by neutron star mergers in cosmological simulations of a Milky Way-mass galaxy
• s-Process Nucleosynthesis in Advanced Burning Phases of Massive Stars
• The role of neutron star mergers in the chemical evolution of the Galactic halo
• The Branchings of the Main s-process: Their Sensitivity to alpha-induced Reactions on 13C and 22Ne and to the Uncertainties of the Nuclear Network
• Barium Isotopic Composition of Mainstream Silicon Carbides from Murchison: Constraints for s-Process Nucleosynthesis in AGB Stars
• Heavy elements in Globular Clusters: the role of AGB stars
• Experimental evidence of a natural parity state in ${}^{26}$Mg and its impact to the production of neutrons for the s process

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