The C12(α,γ)O16

Abstract

The creation of carbon and oxygen in our universe is one of the forefront questions in nuclear astrophysics. The determination of the abundance of these elements is key to both our understanding of the formation of life on earth and to the life cycles of stars. While nearly all models of different nucleosynthesis environments are affected by the production of carbon and oxygen, a key ingredient, the precise determination of the reaction rate of 12 C(α, γ) 16 O, has long remained elusive. This is owed to the reaction's inaccessibility, both experimentally and theoretically. Nuclear theory has struggled to calculate this reaction rate because the cross section is produced through different underlying nuclear mechanisms. Isospin selection rules suppress the E1 component of the ground state cross section, creating a unique situation where the E1 and E2 contributions are of nearly equal amplitudes. Experimentally there have also been great challenges. Measurements have been pushed to the limits of state of the art techniques, often developed for just these measurements. The data have been plagued by uncharacterized uncertainties, often the result of the novel measurement techniques, that have made the different results challenging to reconcile. However, the situation has markedly improved in recent years, and the desired level of uncertainty, ≈10%, may be in sight. In this review the current understanding of this critical reaction is summarized. The emphasis is placed primarily on the experimental work and interpretation of the reaction data, but discussions of the theory and astrophysics are also pursued. The main goal is to summarize and clarify the current understanding of the reaction and then point the way forward to an improved determination of the reaction rate.

Recent Results from ISOLDE and HIE-ISOLDE

“…At this energy the cross section is too low to be measured directly at the laboratory, and it has to be extrapolated. The present cross section estimate at this energy has an error of 20% while the desired precision is of 10 % [2]. The -delayed alpha emission of 16 N has proven to be a good indirect method as it allows for the determination of the E1 On the left hand side, a photo (courtesy of R. Lica) of the charged particle setup used at IDS, ISOLDE to study the ↵ spectrum of the 16 N decay.…”

Astronuclear Physics: A tale of the atomic nuclei in the skies

“…Another reaction of importance in the He-burning process is 12 C (α , γ) 16 O which has been at the focus of a flurry of experimental and theoretical efforts. The reader is referred to [341] for a review of experiments and theory, and to e.g. [248,342] for experimental approaches (see also Section 5.5.1).…”

Chromium Nucleosynthesis and Silicon–Carbon Shell Mergers in Massive Stars

“…There are several sources of uncertainties in generating grids of stellar models for GCE applications, including, for example, uncertainties in nuclear reaction rates (e.g., Lugaro et al 2004;Tur et al 2009;Travaglio et al 2014;deBoer et al 2017;Nishimura et al 2017;Denissenkov et al 2018;Fields et al 2018), stellar evolution and internal mixing (e.g., Meakin & Arnett 2007;Sukhbold & Woosley 2014;Jones et al 2015;Davis et al 2019), and supernova explosion modeling (e.g., Sukhbold et al 2016;Fryer et al 2018;Couch et al 2019;Ebinger et al 2019;Müller 2019). Turning this argument around, GCE studies are ideal framework to explore the impact of stellar processes in a broader astronomical context (Côté et al 2017).…”