Study of proton resonances in 18Ne via resonant elastic scattering of 17F + p and its astrophysical implication in the stellar reaction of 14O(α, p)17F

Abstract

The stellar 14O (α, p) 17F reaction is thought to be one of the most important breakout reactions from the Hot CNO cycles into the rp-process in Type I X-ray bursters. In the present work, the properties of proton resonances in 18Ne have been investigated efficiently by utilizing a technique of proton resonant elastic scattering with a 17F radioactive-ion (RI) beam and a thick proton target. A 4.22 MeV/nucleon 17F RI beam, which was produced via a projectile-fragmentation reaction and experiencing a series of energy degradation, was separated by a Radioactive Ion Beam Line in Lanzhou (RIBLL) and bombarded a (CH2)n target. Energy spectra of the recoiled protons were measured by two sets of ΔE-E silicon telescope at center-of-mass scattering angles of θ c.m. ≈ 175° ± 5°, θ c.m. ≈ 152° ± 8°, respectively. Several proton resonances in 18Ne were observed, and their resonant parameters have been determined by an R-matrix analysis of the differential cross-sections. A doublet structure around 7.10 MeV has been identified and thought to be one state at 7.05 MeV (2+) and another one at 7.12 MeV (4+). The presently calculated total reaction rates of 14O (α, p) 17F are, at least, a factor of 1.2 ∼ 1.9 larger than the previous ones in a temperature region of 1.7 ∼ 3.0 GK mainly owing to the contribution from the 7.05 MeV (2+) state. This result implies that this breakout reaction may play a more important role than previously expected.