No abstract

The neutron capture cross section of 14 C is of relevance for several nucleosynthesis scenarios such as inhomogeneous Big Bang models, neutron induced CNO cycles, and neutrino driven wind models for the r process. The 14 C(n, γ ) reaction is also important for the validation of the Coulomb dissociation method, where the (n, γ ) cross section can be indirectly obtained via the time-reversed process. So far, the example of 14 C is the only case with neutrons where both, direct measurement and indirect Coulomb dissociation, have been applied. Unfortunately, the interpretation is obscured by discrepancies between several experiments and theory. Therefore, we report on new direct measurements of the 14 C(n, γ ) reaction with neutron energies ranging from 20 to 800 keV.

The 7Li(n, c)8Li reaction has relevance for primordial nucleosynthesis in inhomogeneous big bang models as well as in connection with the solar neutrino problem, where the mirror reaction 7Be(p, c)8Be is responsible for the production of high-energy solar neutrinos. The cross section was measured at neutron energies of meV and keV. With the present results and a reanalysis of a previous E n \ 5 E n \ 54 measurement, the discrepancies among existing data could be resolved and the cross section can be determined with improved accuracy.

No abstract

Angular distributions of 12C(alpha,alpha)12C have been measured for E(alpha) = 2.6-8.2 MeV, at angles from 24 to 166, yielding 12 864 data points. R-matrix analysis of the ratios of elastic scattering yields a reduced width amplitude of gamma12 = 0.47 +/- 0.06 MeV(1/2) for the Ex = 6.917 MeV (2+) state in 16O(a = 5.5 fm). The dependence of the chi2 surface on the interaction radius a has been investigated and a deep minimum is found at a = 5.42(+0.16)(-0.27) fm. Using this value of gamma12, radiative alpha capture and 16N beta-delayed alpha-decay data, the S factor is calculated at E(c.m.) = 300 keV to be S(E2)(300) = 53(+13)(-18) keV b for destructive interference between the subthreshold resonance tail and the ground state E2 direct capture.