Redetermination of the neutron scattering length of holmium

An attempt to determine accurately the neutron scattering length of holmium from Ho₂O₃ and Ho₂O₂S powders did not give accurate results. It indicated however that the currently accepted value b_Ho = 8.5 × 10^-12 mm was too high. A very precise determination was possible with a HoAl₂ single crystal and polarized neutrons. The new value is b_Ho = 8.08 (5) × 10^-12 mm.