Köln 2004 – wissenschaftliches Programm

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HK: Physik der Hadronen und Kerne

HK 34: Nuclear and Particle Astrophysics II

HK 34.7: Vortrag

Mittwoch, 10. März 2004, 15:45–16:00, F

A measurement of the ¹⁴C(n,γ)¹⁵C reaction with the fast cyclic activation technique — •F. Käppeler¹, J. Görres², R.C. Haight³, M. Heil¹, R. Plag¹, R. Reifarth³, R.S. Rundberg³, M. Wiescher², and J.B. Wilhelmy³ — ¹Forschungszentrum Karlsruhe, Institut für Kernphysik, Postfach 3640, D-76021 Karlsruhe, Germany — ²Department of Physics, University of Notre Dame, Notre Dame, IN 46556, USA — ³Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA

Inhomogeneous big bang models offer a possibility to bridge the mass gaps at A=5 and 8 via the reaction sequence ⁷Li(n,γ)⁸Li(α,n)¹¹B(n,γ) ¹²B(β⁻)¹²C. Subsequent neutron captures ¹²C(n,γ)¹³C(n,γ)¹⁴C will then lead to the production of ¹⁴C which has a half-life of 5730 years. On the time scale of big bang nucleosynthesis ¹⁴C can be considered as stable and further proton, alpha, deuteron, and neutron capture reactions on ¹⁴C will result in the production of heavier nuclei (A≥20). Due to the high neutron abundance it is expected that the ¹⁴C(n,γ) reaction competes strongly with the other reactions. The ¹⁴C(n,γ) reaction is also important to validate (n,γ) cross sections obtained via the inverse reaction by the Coulomb breakup method. ¹⁴C is one of the few nuclei where the (n,γ) reaction can be measured directly and compared with results of Coulomb breakup experiments, in this case on the neutron-rich isotope ¹⁵C. In this contribution we report on new measurements of the ¹⁴C(n,γ) reaction at neutron energies of 30, 150, and 500 keV using the fast cyclic activation technique.