Cross sections for 170° backscattering of 4He from oxygen in the energy range of 2.0–9.0 MeV

Thermonuclear rate for theF19(α,p)Ugalde1, Azuma2, Couture3 et al. 2008Phys. Rev. C294331View full textAdd to dashboardCite

“…Both a proton or an α-particle can be captured by 18 O. In the former case, 4 He and 15 N are being produced, whereas in the latter case 22 Ne is formed. This second possibility does not produce fluorine.…”

“…Because of the high abundance of 4 He in the intershell region, the 19 F(α, p) 22 Ne is expected to be a dominant depletion link. Another depletion process corresponds to the 19 F(n, γ ) 20 F reaction, caused by neutrons being produced by the 13 C(α, n) 16 O or the 22 Ne(α, n) 25 Mg reactions. If hydrogen is available in sufficient abundance, fluorine may also be depleted through the very strong 19 F(p, α) 16 O reaction.…”

“…The reaction rate for 19 F(α, p) 22 Ne is highly uncertain at helium-burning temperatures. Even recent nucleosynthesis simulations [7] still rely on the very simplified rate expression of Caughlan and Fowler (CF88) [8] based on an optical model approximation for estimating the cross section of compound nuclear reactions with overlapping resonances.…”

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The 19 F(α, p) 22 Ne reaction is considered to be one of the main sources of fluorine depletion in AGB and Wolf-Rayet stars. The reaction rate still retains large uncertainties due to the lack of experimental studies available.

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Composition, nanostructure, and optical properties of silver and silver-copper lusters

“…29 A 3035 keV energy He-beam with square-section (1 mm in diagonal) was used thus taking advantage of the elastic resonance 16 O(a,a) 16 O occurring at this energy 30 and increasing the sensitivity to oxygen concentration by a factor of 23. The samples were kept in vacuum.…”