Re-evaluation of the $^{22}$Ne($p$,$\gamma$)$^{23}$Na reaction rate: $R-$matrix analysis of the non-resonant capture and effect of the 8945 keV (${7/2}^{-}$) resonance strength

TL;DR

This study re-evaluates the $^{22}$Ne($p$,$ extgamma$)$^{23}$Na reaction rate using R-matrix analysis, transfer reaction data, and shell model calculations, revealing a higher rate that impacts stellar nucleosynthesis models.

Contribution

It provides a new, more accurate reaction rate by combining R-matrix analysis, transfer reaction data, and shell model calculations, improving previous estimates for astrophysical applications.

Findings

Reaction rate is approximately 15% higher at relevant temperatures.

Enhanced ANC value leads to increased non-resonant S-factor.

Resonance strengths of 8945 keV doublets are quantified.

Abstract

The $^{22}$Ne($p,\gamma$)$^{23}$Na capture reaction is a key member of the Ne-Na cycle of hydrogen burning. The rate of this reaction is critical in classical novae nucleosynthesis and hot bottom burning processes (HBB) in asymptotic giant branch (AGB) stars. Despite its astrophysical importance, significant uncertainty remains in the reaction rate due to several narrow low energy resonances lying near the Gamow window. The present work revisits this reaction by examining the contribution of the 8664 keV subthreshold state and the 151 keV doublet resonance state of 7/2$^-$ configuration in $^{23}$Na. Finite range distorted-wave Born approximation (FRDWBA) analyses of existing $^{22}$Ne($^3$He,$d$)$^{23}$Na transfer reaction data were carried out to extract the peripheral asymptotic normalization coefficients (ANC) of the 8664 keV state. The ANC value obtained in the present work is $\sim 25\%$ higher compared to the previous work by Santra et al.~\cite{SA20}. Systematic $R$-matrix calculations were performed to obtain the non-resonant astrophysical $S$-factor utilizing the enhanced ANC value. The resonance strengths of the 8945 keV doublets were deduced from shell model calculations. The total reaction rate is found to be $\sim 15\%$ higher at temperatures relevant for the HBB processes, compared to the recent rate measured by Williams et al.~\cite{WI20}, and matches the rate by Williams et al.~\cite{WI20} at temperatures of interest for classical novae nucleosynthesis.