$R$-matrix analysis of ${}^{22}$Ne($\alpha$, n)${}^{25}$Mg and ${}^{22}$Ne($\alpha$, $\gamma$)${}^{26}$Mg reaction

Abstract

The ${}^{22}$Ne($\alpha$, n)${}^{25}$Mg and its competing channel ${}^{22}$Ne($\alpha$, $\gamma$)${}^{26}$Mg has an major influence on neutron flux in weak s-process nucleosynthesis path in low mass AGB stars and massive stars of mass (M$\ge$ 10M${}_{\odot }$). So the ratio rate of this two competing reaction control the neutron flux in weak s-process nucleosynthesis. Various experiment has been performed to study the properties of nuclear states of ${}^{26}$Mg to evaluate rate of ${}^{22}$Ne+$\alpha$ reaction rate and corresponding rate from these studies vary by up to a factor of 500 in the astrophysical relevant temperature. The recent evaluation by Philip et al. of ${}^{22}$Ne($\alpha$, n)${}^{25}$Mg reaction rate using most recent nuclear data of ${}^{26}$Mg from number of sources shows similar result with previous estimation for ${}^{22}$Ne($\alpha$, $\gamma$)${}^{26}$Mg but got lower rate for ${}^{22}$Ne($\alpha$, n)${}^{25}$Mg reaction due to updated nuclear data. Also Philip et al. suggested that rate based on full $R$-matrix modeling will required to take into accounted the interference effects between distant levels and sub-threshold resonance. In present work full $R$-matrix calculation has been performed for ${}^{22}$Ne($\alpha$, n)${}^{25}$Mg and ${}^{22}$Ne($\alpha$, $\gamma$)${}^{26}$Mg reaction based on fitting the ${}^{22}$Ne($\alpha$, n)${}^{25}$Mg reaction data of Jaeger et al; in energy range 0.8 to 1.45 MeV and updated nuclear data of ${}^{26}$Mg states. The $R$-matrix fitting for the ${}^{22}$Ne($\alpha$, n)${}^{25}$Mg reaction nicely explain experimental data in 0.8 to 1.45 MeV energy range by changing spin, parity of E${}_x$ = 11.784 and 11.63 MeV states from 1${}^{-}$ to 0${}^{+}$.