Measurement of the O-14(alpha, p)F-17 cross section at E-c.m. approximate to 2.1-5.3 MeV

Abstract

Background: The O-14(alpha, p)F-17 reaction plays an important role as the trigger reaction for the x-ray burst. Purpose: The direct measurement of O-14(alpha, p)F-17 was made for studying the resonant states in Ne-18 and determining the reaction rate of O-14(alpha, p)F-17 at astrophysical temperatures. Methods: The differential cross section of the O-14(alpha, p)F-17 reaction was measured using a 2.5-MeV/u O-14 radioactive beam and the thick target method in inverse kinematics. Three sets of Delta E-E Si telescopes were installed and coincidence measurements were performed. We analyzed single-proton decay events using the time-of-flight (TOF) information of the recoiling protons. Results: The excitation function of O-14(alpha, p)F-17 was acquired for excitation energies between 7.2 and 10.4 MeV in Ne-18 by considering the two channels which decay to the ground state and first excited state of F-17. Several new, as well as previously known, states in Ne-18 were observed and their resonance parameters were extracted from R-matrix analysis. The contributions of four resonances over the excitation energy range, 7 < E-x < 8.2 MeV, to the O-14(alpha, p)F-17 reaction rate were calculated. Conclusions: We observed very strong single-proton decay events, but did not observe strong double-proton decay events as in a previous study by Fu et al. The reaction rates contributed by the 7.35-, 7.58-, and 7.72-MeV states were estimated to be dominant at temperatures T-9 > 2. Among these three states, the 7.35-MeV state was found to enhance the reaction rate by a factor of 10 greater than the other two resonance states.