Resonances in 19Ne with relevance to the astrophysically important 18F(p,{\alpha})15O reaction

TL;DR

This study measures resonances in 19Ne relevant to the 18F(p,α)15O reaction, crucial for understanding gamma-ray signals from novae, revealing new broad states that impact astrophysical models.

Contribution

It provides new experimental data and R-Matrix analysis of resonances in 19Ne, identifying a broad 1/2+ state affecting the reaction rate in astrophysical environments.

Findings

Identification of resonances consistent with previous data

Observation of extra strength above 1.3 MeV in both reactions

Detection of a broad 1/2+ state influencing reaction rates

Abstract

The most intense gamma-ray line observable from novae is likely to be from positron annihilation associated with the decay of 18F. The uncertainty in the destruction rate of this nucleus through the 18F(p,{\alpha})15O reaction presents a limit to interpretation of any future observed gamma-ray flux. Direct measurements of the cross section of both this reaction and the 18F(p,p)18F reaction have been performed between center of mass energies of 0.5 and 1.9 MeV. Simultaneous fits to both data sets with the R-Matrix formalism reveal several resonances, with the inferred parameters of populated states in 19Ne in general agreement with previous measurements. Of particular interest, extra strength has been observed above ECM \sim1.3 MeV in the 18F(p,p)18F reaction and between 1.3-1.7 MeV in the 18F(p,{\alpha})15O reaction. This is well described by a broad 1/2+ state, consistent with both a recent theoretical prediction and an inelastic scattering measurement. The astrophysical implications of a broad sub-threshold partner to this state are discussed.