Abstract
After an improvement on the theory of the neutron-gravity-refractometer and after refinements of the experimental procedure we have performed new measurements of the absolute value of the neutron-proton scattering amplitude at low neutron energies. In order to obtain and to confirm a very high accuracy we carried out neutron-reflection experiments on 18 various liquids of 11 different organic substances containing the elements carbon, hydrogen and/or chlorine. Compounds with fluorine and bromine were used to measure the scattering amplitudes of these elements.
We found the coherent scattering amplitudes of the bound atoms to be:a H=−3.7409(1l)fm,a c=6.6484(13)fm,a c1=9.5792(8)fm,a F=5.66(2)fm anda Br=6.79(2)fm.
The low energy (n, p)-parametersa t anda s were calculated with the presenta H and a new value of the (n, p) scattering cross-sectionσ 0.
By comparing the measureda C with values obtained from precise transmission experiments we could determine the gravitational accelerationg f of the free neutron in terms of the local value g. We found the two values to be equal:g f =0.9996(7)g.
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We wish to acknowledge helpful discussions with N. Nücker and W. D. Trüstedt. They made essential contributions to the theory and to the evaluation of the measurements. We are very thankful to Prof. H.J. Born, who gave us the opportunity to perform the important gas-chromatography in his radiochemical institute. We thank for the helpful assistance of J. Bruckmoser and the reactor staff.
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Koester, L., Nistler, W. New determination of the neutron-proton scattering amplitude and precise measurements of the scattering amplitudes on carbon, chlorine, fluorine and bromine. Z Physik A 272, 189–196 (1975). https://doi.org/10.1007/BF01408146
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DOI: https://doi.org/10.1007/BF01408146