Neutron capture measurements of the noble gas isotopes 22Ne, 40Ar and 78,80,84,86Kr in the keV energy region

At the Karlsruhe and Tubingen 3.75 MV Van de Graaff accelerators the cross sections of Ne-22(n, gamma)Ne-23 (37.2 s), Ar-40(n, gamma)Ar-41 (1.83 h), and the Kr isotopes Kr-78(n, gamma)Kr-79(m) (50 s), Kr-78(n, gamma)Kr-79(35.04 h), Kr-80(n, gamma)Kr-81(m) (13.1 s), Kr-84(n, gamma)Kr-85(m) (4.48 h),and Kr-86(n, gamma)Kr-87 (76.3 m), were measured in the keV energy range by the regular and/or the fast cyclic activation techniques via the characteristic gamma-ray lines in the decay of the respective residual nuclei. High pressure gas samples which consisted of Ne-22-Kr and Ar-40-Kr mixtures were irradiated using the Li-7(p, n) and T(p, n) reactions. The measurements were carried out at the neutron energies 25, 30, 52, 104, 149, 180, and 215 keV. Stellar reaction rates for thermal energies kT between 1 and 250 keV were determined. The population probability of the Kr-85(m) isomeric state by neutron capture of Kr-84 was studied as a function of neutron energy. No significant energy dependence was found. (C) 2002 Elsevier Science B.V. All rights reserved.