Measurement of the Electron-Neutron Interaction by the Asymmetrical Scattering of Thermal Neutrons by Noble Gases

The electron-neutron interaction has been obtained from measurements of thermal neutron scattering by argon, krypton, and xenon. In terms of the slope of the electric structure factor of the neutron at zero momentum transfer, the values obtained were 0.0196\ifmmode\pm\else\textpm\fi{}0.0013 ${\mathrm{F}}^{2}$ from Ar, 0.0197\ifmmode\pm\else\textpm\fi{}0.0007 ${\mathrm{F}}^{2}$ from Kr, and 0.0190\ifmmode\pm\else\textpm\fi{}0.0005 ${\mathrm{F}}^{2}$ from Xe. The final result is 0.0193\ifmmode\pm\else\textpm\fi{}0.0004 ${\mathrm{F}}^{2}$, which corresponds to an electron-neutron scattering length of -1.34\ifmmode\pm\else\textpm\fi{}0.03\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}16}$ cm and an effective potential of -3720\ifmmode\pm\else\textpm\fi{}90 eV. During the course of the experiment, the neutron-absorption cross sections of krypton and xenon (at 2200 m/sec) were measured by transmission and found to be 25.0\ifmmode\pm\else\textpm\fi{}0.8 b and 25.1\ifmmode\pm\else\textpm\fi{}1.0 b, respectively. Also, some free-atom thermal-neutron scattering cross sections were measured. The results were 2.415\ifmmode\pm\else\textpm\fi{}0.010 b for neon, 0.647\ifmmode\pm\else\textpm\fi{}0.003 b for argon, 7.61\ifmmode\pm\else\textpm\fi{}0.04 b for krypton, 4.30\ifmmode\pm\else\textpm\fi{}0.02 b for xenon, 73.7\ifmmode\pm\else\textpm\fi{}0.4 b for $^{36}\mathrm{Ar}$, 1.705\ifmmode\pm\else\textpm\fi{}0.009 b for $^{22}\mathrm{Ne}$, and 5.1\ifmmode\pm\else\textpm\fi{}0.3 b for $^{21}\mathrm{Ne}$.