Eur. Phys. J. A (2025) 61: 70
https://doi.org/10.1140/epja/s10050-025-01537-1

Review

The $_{}^{12}$C${(\alpha ,\gamma )}^{16}$O reaction, in the laboratory and in the stars

¹ Department of Physics and Astronomy, University of Notre Dame, 46556, Notre Dame, IN, USA
² Dipartimento di Fisica “E. Pancini”, Università degli Studi di Napoli “Federico II”, Via Cintia, 80126, Naples, Italy
³ INFN, Sezione di Napoli, Via Cintia, 80126, Naples, Italy
⁴ Department of Physics and Astronomy, Ohio University, 45701, Athens, OH, USA
⁵ Istituto Nazionale di Astrofisica-Istituto di Astrofisica e Planetologia Spaziali, Via Fosso del Cavaliere 100, 00133, Rome, Italy
⁶ Monash Centre for Astrophysics (MoCA), School of Mathematical Sciences, Monash University, 3800, Melbourne, VIC, Australia
⁷ INFN, Sezione di Perugia, via A. Pascoli s/n, 06125, Perugia, Italy
⁸ Université Paris-Saclay, CNRS/IN2P3, IJCLab, 91405, Orsay, France
⁹ Facility for Rare Isotope Beams, Michigan State University, 48824, East Lansing, MI, USA
¹⁰ Department of Physics and Astronomy, Michigan State University, 48824, East Lansing, MI, USA
¹¹ China Institute of Atomic Energy, P.O. Box 275(10), 102413, Beijing, China
¹² Department of Physics, Southern University of Science and Technology, 518055, Shenzhen, China
¹³ School of Earth and Space Exploration, Arizona State University, 85287, Tempe, AZ, USA

^a rdeboer1@nd.edu

Received: 20 December 2024
Accepted: 2 March 2025
Published online: 1 April 2025

Abstract

The evolutionary path of massive stars begins at helium burning. Energy production for this phase of stellar evolution is dominated by the reaction path 3$\alpha {\to }^{12}$ C${(\alpha ,\gamma )}^{16}$O and also determines the ratio of $_{}^{12}$C/$_{}^{16}$O in the stellar core. This ratio then sets the evolutionary trajectory as the star evolves towards a white dwarf, neutron star or black hole. Although the reaction rate of the 3$\alpha$ process is relatively well known, since it proceeds mainly through a single narrow resonance in $_{}^{12}$C, that of the $_{}^{12}$C${(\alpha ,\gamma )}^{16}$O reaction remains uncertain since it is the result of a more difficult to pin down, slowly-varying, portion of the cross section over a strong interference region between the high-energy tails of subthreshold resonances, the low-energy tails of higher-energy broad resonances and direct capture. Experimental measurements of this cross section require herculean efforts, since even at higher energies the cross section remains small and large background sources are often present that require the use of very sensitive experimental methods. Since the $_{}^{12}$C${(\alpha ,\gamma )}^{16}$O reaction has such a strong influence on many different stellar objects, it is also interesting to try to back calculate the required rate needed to match astrophysical observations. This has become increasingly tempting, as the accuracy and precision of observational data has been steadily improving. Yet, the pitfall to this approach lies in the intermediary steps of modeling, where other uncertainties needed to model a star’s internal behavior remain highly uncertain.