Searching for resonance states in 22Ne(p, γ) 23Na

Background: Globular clusters show strong correlations between different elements, such as the well-known sodium-oxygen anticorrelation. One of the main sources of uncertainty in this anticorrelation is the 22Ne(p, gamma) 23Na reaction rate, due to the possible influence of an unobserved resonance state at Ex = 8862 keV (Er,c.m. = 68 keV). The influence of two higher-lying resonance states at Ex = 8894 and 9000 keV has already been ruled out by direct 22Ne(p, gamma) 23Na measurements.Purpose: The purpose of this paper is to study excited states in 23Na above the proton threshold to determine if the unconfirmed resonance states in 23Na exist.Methods: The nonselective proton inelastic-scattering reaction at low energies was used to search for excited states in 23Na above the proton threshold. Protons scattered from various targets were momentum-analyzed in the Q3D magnetic spectrograph at the Maier-Leibnitz Laboratorium, Munich, Germany.Results: The resonance states previously reported at Ex = 8862, 8894, and 9000 keV in other experiments were not observed in the present experiment at any angle. This result, combined with other nonobservations of these resonance states in most other experiments, results in a strong presumption against the existence of these resonance states.Conclusions: The previously reported resonance states at Ex = 8862, 8894, and 9000 keV are unlikely to exist and should be omitted from future evaluations of the 22Ne(p, gamma) 23Na reaction rates. Indirect studies using low-energy proton inelastic scattering are a simple and yet exceptionally powerful tool in helping to constrain astrophysical reaction rates by providing nonselective information of the excited states of nuclei.