Is γ-ray emission from novae affected by interference effects in the 18F(p,α)15O reaction?

Area of Science:

• Nuclear astrophysics
• Stellar nucleosynthesis
• Radioactive ion beam physics

Background:

• The reaction rate of Fluorine-18 (¹⁸F) is critical for predicting gamma-ray emissions from novae.
• Previous studies faced significant uncertainty due to interference effects in the compound nucleus ¹⁹Ne, impacting the ¹⁸F production rate.
• A broad J(π)=3/2(+) state near the proton threshold was thought to be the main source of uncertainty.

Purpose of the Study:

• To investigate the level scheme of ¹⁹Ne near the proton threshold.
• To resolve the dominant uncertainty in the ¹⁸F(p,α)¹⁵O reaction rate.
• To refine astrophysical models of nova nucleosynthesis and ¹⁸F production.

Main Methods:

• Utilized the ¹⁹F((3)He,t)¹⁹Ne reaction to probe energy levels in ¹⁹Ne.
• Analyzed angular distributions of newly identified resonances.
• Incorporated findings into hydrodynamic nova model calculations.

Main Results:

• Discovered at least three new resonances between the proton threshold and E(cm)=50 keV.
• Observed distinct angular distributions for these resonances, inconsistent with J(π)=3/2(+).
• Identified the unknown proton width of the 48 keV resonance as the primary uncertainty, not interference effects.

Conclusions:

• Re-evaluated the dominant uncertainty in the ¹⁸F(p,α)¹⁵O reaction rate.
• The new findings reduce the uncertainty stemming from interference effects.
• The unknown proton width of the 48 keV resonance introduces at least a factor of two uncertainty in ¹⁸F production in nova models.