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

TL;DR

This paper performs a comprehensive R-matrix analysis of the $^{22}$Ne($ ext{α}$, n)$^{25}$Mg and $^{22}$Ne($ ext{α}$, γ)$^{26}$Mg reactions, crucial for understanding neutron flux in stellar nucleosynthesis, updating nuclear data and resonance parameters.

Contribution

The study introduces a full R-matrix calculation incorporating interference effects and updated nuclear data, refining reaction rates relevant for astrophysical models.

Findings

R-matrix fits explain experimental data well in 0.8-1.45 MeV range.

Revised spin and parity assignments for specific nuclear states.

Updated reaction rates impact neutron flux estimates in stellar environments.

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$\geq$ 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$^+$.