Properties of states near $E_x$ = 6 MeV in $^{18}$Ne through $^{17}$F+p scattering

TL;DR

This study investigates the properties of states near 6 MeV in $^{18}$Ne using $^{17}$F+p scattering, revealing two possible spin-parity assignments that significantly affect the $^{14}$O($eta$,p)$^{17}$F reaction rate relevant for astrophysical processes.

Contribution

The paper provides new experimental data and analysis on $^{18}$Ne states near 6 MeV, offering two possible spin-parity solutions that impact astrophysical reaction rates.

Findings

Identified a state at 6.14 MeV with ambiguous spin-parity assignment.

Reanalyzed previous data to support a consistent set of resonance parameters.

Reaction rate estimates vary by up to an order of magnitude depending on the assignment.

Abstract

Background: The rate of energy production in the hot-CNO cycle and breakout to the rapid-proton capture process in Type I X-ray bursts is strongly related to the $^{14}$O($\alpha,p$)$^{17}$F reaction rate. The properties of states in $^{18}$Ne near $E_x=6.1-6.3$ MeV are important for understanding this reaction rate. Experiment: The RESOLUT radioactive-ion beam facility at Florida State University was used to study $^{18}$Ne resonances around this energy region using $^{17}$F(p,p)$^{17}$F elastic scattering on a polypropylene target under inverse kinematics. Scattered protons were detected in a silicon-strip detector array while recoiling $^{17}$F ions were detected in coincidence in a gas ionization detector. Analysis: An $R$-matrix analysis of measured cross sections was conducted along with a reanalysis of data from previous measurements. Results: All the data analyzed are well described by a consistent set of parameters with with a $1^-$ assignment for a state at 6.14(1) MeV. A second comparable solution is also found with a $3^-$ assignment for the 6.14(1) MeV state. The rate of the $^{14}$O($\alpha$,p)$^{17}$F reaction that is determined from the two solutions differs by up to an order of magnitude.