We have measured the neutron electric form factor $G_{\mathrm{en}}$ via ${}^3\overrightarrow{\mathrm{He}}\left(\overrightarrow{e}{,e}^{\prime }n\right)\mathrm{pp}$ at $Q^2=0.67\mathrm{}(\mathrm{GeV}/c{)}^2$ using the 3-spectrometer facility of the A1 Collaboration at the Mainz Microtron and a dedicated neutron detector. High pressure polarized ${}^3\overrightarrow{\mathrm{He}}$ gas was used as a target of polarized neutrons. $G_{\mathrm{en}}$ is determined from the ratio of the asymmetries $A_{\perp }{/A}_{\parallel }$ measured in quasifree kinematics with the target spin perpendicular and parallel to the momentum transfer. We find $G_{\mathrm{en}}=0.052\mathrm{}\pm 0.011\pm 0.005$.

• Received 30 April 1999

DOI:https://doi.org/10.1103/PhysRevLett.83.4257