C12(α,γ)16O

The C12(α,γ)O16deBoer1, Görres2, Wiescher3 et al. 2017Rev. Mod. Phys.19881431View full textAdd to dashboardCite

“…A thick target (450 µg/cm 2 ) technique was used and measurements were made over an α energy range from 3.00 to 3.45 MeV. These measurements were associated with decays of γ rays from the E x = 9.59 MeV state, whose γ decay width was of great interest at the Ouellet et al (1996Ouellet et al ( , 1992 ion implantation Au 3-5×10 18 atoms/cm 2 factor of 10 3 13 C depletion Roters et al (1999) He gas target 9.1 Torr 0.0001% Gialanella et al (2001) He gas target 20 Torr 0.0001% Kunz et al (2001) ion implantation Au 2-3×10 18 atoms/cm 2 factor of 10 3 13 C depletion Fey (2004) ion 16 O reaction (this work) to that of the 13 C(α, n) 16 O reaction. Because of the large difference in cross sections, even trace amounts of 13 C in target materials and beam line elements can create large backgrounds in the γ-ray spectra of 12 C(α, γ) 16 O measurements.…”

“…The data was first reported in Ouellet et al (1992) but results were subsequently revised in Ouellet et al (1996). The experiment was performed in forward kinematics using water cooled implanted targets very similar to those of Redder et al (1987).…”

Nuclear astrophysics with secondary (Radioactive) beams

“…This reaction is governed by the quantum mechanical tail of the bound 2 + at 6.92 MeV, and the interference of the tail of the bound 1 − state at 7.12 MeV and the tail of the quasi-bound 1 − state at 9.63 MeV in 16 O. These effects eluded measurements of the cross section (and the S-factor = Eσexp(2πη) and η = e 2 Z 1 Z 2 /hv) of the 12 C(α, γ) 16 O reaction for the last two decades, in spite of repeated attempts [4,5,6,7,8], and was only recently measured using the time reverse process of the disintegration of 16 O, populated in the beta-decay of 16 N [9, 10, 11, 12, 13, 14]. Helium burning lasts for approximately 500,000 years in a 25 solar masses star [2,3], and occurs at temperatures of approximately 200 MK.…”

“…8 Be(α, γ) 12 C. The formation of small concentration of 8 Be, allows for a larger phase space for the triple alpha-capture reaction to occur. This reaction was originally proposed by sir Fred Hoyle in the 50's, as a solution for bridging the gap over the mass 5 and 8, where no stable elements exist, and therefore the production of heavier elements.…”

“…At temperatures of the order of 200 MK [2,3], the burning of helium sets in. The first reaction to occur in helium burning is the α + α → 8 Be, and due to the short lifetime of 8 Be this reaction yield a small concentration of 8 Be nuclei in the star. However, this reaction is very crucial as a stepping stone for the next reaction that is loosely described as the three alphacapture process:…”