Measurement of 1323 and 1487 keV resonances in 15N(α, γ)19F with the recoil separator ERNA

Abstract

The origin of fluorine is a widely debated issue. Nevertheless, the ^{15}N(α,γ)^{19}F reaction is a common feature among the various production channels so far proposed. Its reaction rate at relevant temperatures is determined by a number of narrow resonances together with the DC component and the tails of the two broad resonances at E_{c.m.} = 1323 and 1487 keV. Measurement through the direct detection of the 19F recoil ions with the European Recoil separator for Nuclear Astrophysics (ERNA) were performed. The reaction was initiated by a 15N beam impinging onto a 4He windowless gas target. The observed yield of the resonances at Ec.m. = 1323 and 1487 keV is used to determine their widths in the α and γ channels. We show that a direct measurement of the cross section of the ^{15}N(α,γ)^{19}F reaction can be successfully obtained with the Recoil Separator ERNA, and the widths Γ_γ and Γ_α of the two broad resonances have been determined. While a fair agreement is found with earlier determination of the widths of the 1487 keV resonance, a significant difference is found for the 1323 keV resonance Γ_α . The revision of the widths of the two more relevant broad resonances in the 15N(α,γ)19F reaction presented in this work is the first step toward a more firm determination of the reaction rate. At present, the residual uncertainty at the temperatures of the ^{19}F stellar nucleosynthesis is dominated by the uncertainties affecting the Direct Capture component and the 364 keV narrow resonance, both so far investigated only through indirect experiments.

arXiv comment8 pages, 11 figures. Accepted for publication in PRC

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