Constraining the ${}^{22}$Ne($\alpha$,$\gamma$)${}^{26}$Mg and ${}^{22}$Ne($\alpha$,n)${}^{25}$Mg reaction rates using sub-Coulomb $\alpha$-transfer reactions

Abstract

The ${}^{22}$Ne($\alpha$,$\gamma$)${}^{26}$Mg and ${}^{22}$Ne($\alpha$,n)${}^{25}$Mg reactions play an important role in astrophysics because they have significant influence on the neutron flux during the weak branch of the s-process. We constrain the astrophysical rates for these reactions by measuring partial $\alpha$-widths of resonances in ${}^{26}$Mg located in the Gamow window for the ${}^{22}$Ne+$\alpha$ capture. These resonances were populated using ${}^{22}$Ne(${}^6$Li,d)${}^{26}$Mg and ${}^{22}$Ne(${}^7$Li,t)${}^{26}$Mg reactions at energies near the Coulomb barrier. At these low energies $\alpha$-transfer reactions favor population of low spin states and the extracted partial $\alpha$-widths for the observed resonances exhibit only minor dependence on the model parameters. The astrophysical rates for both the ${}^{22}$Ne($\alpha$,$\gamma$)${}^{26}$Mg and the ${}^{22}$Ne($\alpha$,n)${}^{25}$Mg reactions are shown to be significantly different than the previously suggested values.

Comments: 7 pages, 3 figures, 2 tables