Abstract
The capture reaction4He(12C, γ)16O (E c.m.= 1.34–3.38 MeV) as well as the elastic scattering process4He(12C,12C)4He (E c.m.=1.44–3.38 MeV) have been investigated with the use of an intense12C beam and a windowless and4He recirculating gas target system. The measurements involved two large NaI(T1) crystals in close geometry to an extended gas target, whereby angle-integrated γ-ray yields were obtained. A large area plastic detector was used for the suppression of time-independent background. A search for cascade γ-ray transitions was carried out by coincidence techniques. The measurement of absolute cross sections is also reported. Theoretical fits of the excitation function for the groundstate γ-ray transition requireE1 as well asE2 capture amplitudes, which are of equal importance at stellar energies. This result increases significantly the stellar burning rate of4He(12C, γ)16O and leads to16O as the dominant product at the end of helium burning in massive stars. The observed capture yield to the 6.92 MeV state is dominated by the direct capture mechanism and plays a small role at stellar energies.
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Supported by the Deutsche Forschungsgemeinschaft (Ro 429/13-2)
Supported by the Minister für Wissenschaft und Forschung des Landes Nordrhein-Westfalen
The authors greatly appreciate the help of M. Hilgemaier, W.E. Kieser, A. Krauss and A. Redder during the course of the experiments. We are grateful to K. Brand and the technical staff at the Bochum Dynamitron tandem laboratory for providing high12C beam currents. The travel support to the laboratory at Bochum was provided by the Westfälische Wilhelms Universität and is highly acknowledged. Prof. C.A. Barnes (CalTech) is thanked for the many fruitful discussions at the early phase of the experiments. We would like to thank also Prof. B. Zeitnitz (Kernforschungsanlage Karlsruhe) for the loan of a plastic detector and Dr. L. Wallek for the help in the operation of this detector.
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Kettner, K.U., Becker, H.W., Buchmann, L. et al. The4He(12C, γ)16O reaction at stellar energies. Z Physik A 308, 73–94 (1982). https://doi.org/10.1007/BF01415851
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DOI: https://doi.org/10.1007/BF01415851