Refined interpretation of Christiansen-filter experiments and neutron scattering lengths of the lead-isotopes

A refined interpretation of Christiansen filter experiments is described, which allows for the effects of inhomogeneities in the powder column of the filter. Using this procedure the evaluation of experiments on enriched samples of lead isotopes provided the neutron coherent scattering lengths (in fm) for the separated isotopes: b(204)=10.6±2.0; b(206)=9.23±0.05; b(207)=9.28±0.04 and b(208)=9.50±0.06. The corresponding potential scattering radius R' was obtained by taking account of resonance contributions as earlier used in the determination of the neutron's electric polarizability. The found R'=9.74±0.07 fm is in good agreement with the literature. This confirms the correctness of the used resonance contributions. (orig.)