Neutron scattering length of lithium and boron and their isotopes

Coherent neutron scattering lengths and free cross sections were measured in order to determine the spin dependent scattering lengths of the isotopes of Li and B. The transmission measurements on Li at neutron energies of 0.51 meV, 1.26 eV and 5.19 eV delivered data for the 6Li-abundances in the samples and for the free scattering cross section of 7Li. By means of experiments of 15 different samples of lithium compounds we obtained the complex spin state scattering length for the bound atoms to be: of 6Li: bsub(+)=0.67+-0.14-i(0.08+-0.01) fm; bsub(-)=4.67+-0.17-i(0.62+-0.02) fm and of 7Li:bsub(+)=-4.15+-0.06 fm and bsub(-)=1.00+-0.08 fm. Measurements on 3 boron samples with different enrichments led to for 10B: bsub(+)=4.2+-0.4 fm and bsub(-)=5.2+-0.4 fm and for 11B: bsub(+)=5.6+-0.3 fm and bsub(-)=8.3+-0.3 fm. A review on slow neutron scattering and resonance data shows an over all consistency of all values. (orig.)