Determination of anomalous scattering lengths of samarium for thermal neutrons

Anomalous scattering lengths of natural Sm for thermal neutrons with wavelengths between 0.827 and 1.300 Å have been determined by single-crystal diffraction from a Sm complex of known structure. 140 selected reflections were measured at a temperature of 37 K at each wavelength and b₀ + b' and b" refined in each case. The values obtained are in good agreement with values obtained from a Breit-Wigner calculation using tabulated absorption resonance parameters for ¹⁴⁹Sm. A value of b₀ = 4.3 ± 0.2 fm is deduced from the diffraction experiments.