First measurement of the low-energy direct capture in 20Ne(p, {\gamma})21Na and improved energy and strength of the Ecm = 368 keV resonance

TL;DR

This study provides the first direct measurement of the low-energy capture in 20Ne(p,γ)21Na, refining the reaction rate crucial for astrophysical models, and improves the understanding of the 368 keV resonance's strength.

Contribution

It reports the first measurement of the direct capture contribution below 352 keV and refines the resonance strength at 368 keV, reducing uncertainties significantly.

Findings

Resonance strength measured as 0.112 meV with reduced uncertainty.

Reaction rate is 20% lower at T<0.1 GK than previous estimates.

Results impact models of nucleosynthesis in astrophysical environments.

Abstract

The $\mathrm{^{20}Ne(p, \gamma)^{21}Na}$ reaction is the slowest in the NeNa cycle and directly affects the abundances of the Ne and Na isotopes in a variety of astrophysical sites. Here we report the measurement of its direct capture contribution, for the first time below $E\rm_{cm} = 352$~keV, and of the contribution from the $E^{\rm }_{cm} = 368$~keV resonance, which dominates the reaction rate at $T=0.03-1.00$~GK. The experiment was performed deep underground at the Laboratory for Underground Nuclear Astrophysics, using a high-intensity proton beam and a windowless neon gas target. Prompt $\gamma$ rays from the reaction were detected with two high-purity germanium detectors. We obtain a resonance strength $\omega \gamma~=~(0.112 \pm 0.002_{\rm stat}~\pm~0.005_{\rm sys})$~meV, with an uncertainty a factor of $3$ smaller than previous values. Our revised reaction rate is 20\% lower than previously adopted at $T < 0.1$~GK and agrees with previous estimates at temperatures $T \geq 0.1$~GK. Initial astrophysical implications are presented.