The coherent neutron scattering amplitude of ${\mathrm{B}}_2$${\mathrm{O}}_3$, highly enriched in ${\mathrm{B}}^{11}$, has been measured by the multiple-refraction method. Combination with the coherent scattering amplitude of B measured by the mirror method yields: $a_{{\mathrm{B}}^{11}\mathrm{coh}}=+6.53\mathrm{}\pm 0.35$ F; $a_{{\mathrm{B}}^{10}\mathrm{coh}}=+1.4\mathrm{}\pm 1.5$ F.

• Received 26 July 1965

DOI:https://doi.org/10.1103/PhysRev.146.660