The neutron transmission through a thorogenic liquid ${}^{208}\mathrm{Pb}$ sample 2 in. thick has been measured in the neutron energy range between 0.1 and 360 eV at the ORNL neutron source ORELA. Analyzing the shape of the transmission spectra as a function of neutron energy, agreement was found with the predictions by the atomic form factor. With a sensitivity for the mean squared charge radius of the neutron $〈r_n^2〉$ as high as 3%, a very reliable and also accurate result of $〈r_n^2〉=-0.113\mathrm{}\pm 0.003\pm 0.004{\mathrm{fm}}^2$ was extracted. For the neutron-electron scattering length we obtained $b_{\mathrm{ne}}=(-1.31\mathrm{}\pm 0.03\pm 0.04)\times {10}^{-3\mathrm{}}\mathrm{fm}$.

• Received 24 October 1994

DOI:https://doi.org/10.1103/PhysRevLett.74.2427