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

摘要

The stellar ~(14)O (α, p) ~(17)F 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 ~(18)Ne have been investigated efficiently by utilizing a technique of proton resonant elastic scattering with a ~(17)F radioactive-ion (RI) beam and a thick proton target. A 4.22 MeVucleon ~(17)F 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 (CH_2)_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 ~(14)O (α, p) ~(17)F 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.