Measurement of the Spin-Dependent Part of the Scattering Amplitude of Slow Neutrons onF19Using a Polarized Beam and a Polarized Target

Using a polarized target of Ca${\mathrm{F}}_2$, we have measured the spin-dependent part of the scattering amplitude of slow neutrons on ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$. A value $\beta =a_{+}-a_{-}=-0.135\mathrm{}\pm 0.002$ F was found, 10 times smaller than a recent theoretical estimate. A control experiment measuring $\beta =a_{+}-a_{-}$ for the proton by Bragg scattering on a single crystal of LiH yielded the correct value within experimental error.