Neutron Cross Sections and Scattering Lengths ofCu63andCu65

It is of interest to know whether the thermal-neutron scattering lengths of ${\mathrm{Cu}}^{63}$ or ${\mathrm{Cu}}^{65}$ are significantly different from natural copper. From measurements of the intensity of the (111) reflections of natural and isotopically enriched samples, the scattering lengths of ${\mathrm{Cu}}^{63}$, ${\mathrm{Cu}}^{65}$, and natural Cu are found to be (+0.672±0.015)×${10}^{-12\mathrm{}}$ cm, (+1.109±0.019)×${10}^{-12\mathrm{}}$ cm, and (+0.790±0.023)×${10}^{-12\mathrm{}}$ cm, respectively.