H. Fischer, J. Neuefeind, J.M. Simonson, R. Loidl, H. Rauch:

"New measurements of the coherent and incoherent neutron scattering lengths of";^{13}C

Journal of Physics: Condensed Matter,20(2008), 1 - 14.

The techniques of neutron interferometry and neutron diffraction were used to determine the coherent and incoherent neutron scattering lengths of 13C. From a neutron interferometry

measurement of the optical path difference in liquid samples, 13CS2 versus natCS2, we obtain a bound coherent scattering length of bcoh,13C = 6.542 ± 0.003 fm, which differs appreciably

from the standard tabulated value of 6.19 ± 0.09 fm. The resulting contrast of only 0.106(3) fm with respect to bcoh,natC = 6.6484 ± 0.0013 fm has consequences for neutron diffraction

experiments involving 13C isotopic substitution. Combining our result for bcoh,13C with precise neutron diffraction measurements of the self-scattering intensities of liquid samples, 13CS2

versus natCS2, and 13CO2 versus 12CO2, we deduce a bound incoherent scattering length of bincoh,13C = −0.42 ± 0.24 fm that is consistent with the standard tabulated value of −0.52 ± 0.09 fm. The results presented here have required accurate measurements of small

effects, for which particular attention has been given to the data analysis.

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