First Direct Measurement of the 64.5 keV Resonance Strength in the ^{17}O(p,γ)^{18}F Reaction

Area of Science:

• Nuclear astrophysics
• Stellar nucleosynthesis
• Cosmic chemical evolution

Background:

• The CNO cycle is a primary energy source in stars, driving hydrostatic hydrogen burning.
• The ^{17}O(p,γ)^{18}F reaction rate is critical for understanding stellar evolution and is dominated by a poorly constrained 64.5 keV resonance.

Purpose of the Study:

• To directly measure the resonance strength of the 64.5 keV ^{17}O(p,γ)^{18}F reaction.
• To determine the direct capture contribution at 142 keV.
• To refine models of stellar nucleosynthesis and oxygen isotopic abundances.

Main Methods:

• Utilized a new high-sensitivity experimental setup at the Laboratory for Underground Nuclear Astrophysics (LUNA).
• Performed direct measurements of the ^{17}O(p,γ)^{18}F reaction.
• Analyzed resonance strength and direct capture components.

Main Results:

• The measured resonance strength (ωγ = (30±6stat±2syst) peV) is approximately double previous literature values.
• The proton width was determined to be Γp = (34±7stat±3syst) neV.
• Results align with independent measurements from the ^{17}O(p,α)^{14}N channel.

Conclusions:

• The revised ^{17}O(p,γ)^{18}F reaction rate significantly impacts models of stellar interiors.
• Improved understanding of oxygen isotopic ratios in red giant stars and presolar grains.
• Highlights the importance of precise nuclear physics data for astrophysical interpretations.