Investigation of the thermonuclear 18Ne(alpha, p)21Na reaction rate via resonant elastic scattering of 21Na + p.

Zhang, L. Y. and He, J. J. and Parikh, A. and Xu, S. W. and Yamaguchi, H. and Kahl, D. and Kubono, S. and Mohr, Péter and Hu, J. and Ma, P. and Chen, S. Z. and Wakabayashi, Y. and Wang, H. W. and Tian, W. D. and Chen, R. F. and Guo, B. and Hashimoto, T. and Togano, Y. and Hayakawa, S. and Teranishi, T. and Iwasa, N. and Yamada, Taiichi and Komatsubara, T. and Zhang, Y. H. and Zhou, Xiao-Hong (2014) Investigation of the thermonuclear 18Ne(alpha, p)21Na reaction rate via resonant elastic scattering of 21Na + p. PHYSICAL REVIEW C, 89 (1). ISSN 2469-9985

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Abstract

The 18Ne(α,p)21Na reaction is thought to be one of the key breakout reactions from the hot CNO cycles to the rp-process in type I x-ray bursts. In this work, the resonant properties of the compound nucleus 22Mg have been investigated by measuring the resonant elastic scattering of 21Na+p. An 89 MeV 21Na radioactive beam delivered from the CNS Radioactive Ion Beam Separator bombarded an 8.8 mg/cm2 thick polyethylene (CH2)n target. The 21Na beam intensity was about 2×105 pps, with a purity of about 70% on target. The recoiled protons were measured at the center-of-mass scattering angles of θc.m.≈175.2◦ , 152.2◦ , and 150.5◦ by three sets of ∆E-E telescopes, respectively. The excitation function was obtained with the thick-target method over energies Ex(22Mg)=5.5–9.2 MeV. In total, 23 states above the proton-threshold in 22Mg were observed, and their resonant parameters were determined via an R-matrix analysis of the excitation functions. We have made several new Jπ assignments and confirmed some tentative assignments made in previous work. The thermonuclear 18Ne(α,p)21Na rate has been recalculated based on our recommended spin-parity assignments. The astrophysical impact of our new rate has been investigated through one-zone postprocessing x-ray burst calculations. We find that the 18Ne(α,p)21Na rate significantly affects the peak nuclear energy generation rate, reaction fluxes, as well as the onset temperature of this breakout reaction in these astrophysical phenomena.

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