Study of (${}^6$Li, $d$) and (${}^6$Li, $t$) reactions on ${}^{22}$Ne and implications for $s$-process nucleosynthesis

Abstract

We studied $\hat{I}\pm$ cluster states in ${}^{26}$Mg via the ${}^{22}$Ne(${}^6$Li,$d{\hat{I}}^3$)${}^{26}$Mg reaction in inverse kinematics at an energy of $7$ MeV/nucleon. States between $E_x$ = 4 - 12 MeV in ${}^{26}$Mg were populated and relative $\hat{I}\pm$ spectroscopic factors were determined. Some of these states correspond to resonances in the Gamow window of the ${}^{22}$Ne($\hat{I}\pm$,n)${}^{25}$Mg reaction, which is one of the main neutron sources in the astrophysical $s$-process. We show that $\hat{I}\pm$-cluster strength of the states analyzed in this work have critical impact on s-process abundances. Using our new ${}^{22}$Ne($\hat{I}\pm$,n)${}^{25}$Mg and ${}^{22}$Ne($\hat{I}\pm$,${\hat{I}}^3$)${}^{26}$Mg reaction rates, we performed new s-process calculations for massive stars and Asymptotic Giant Branch stars and compared the resulting yields with the yields obtained using other ${}^{22}$Ne+$\hat{I}\pm$ rates from the literature. We observe an impact on the s-process abundances up to a factor of three for intermediate-mass AGB stars and up to a factor of ten for massive stars. Additionally, states in ${}^{25}$Mg at $E_x$ $<$ 5 MeV are identified via the ${}^{22}$Ne(${}^6$Li,$t$)${}^{25}$Mg reaction for the first time. We present the (${}^6$Li, $t$) spectroscopic factors of these states and note similarities to the $(d,p$) reaction in terms of reaction selectivity.