  We experimentally demonstrate that electrically neutral particles, neutrons,
can be used to directly visualize the electrostatic field inside a target
volume that can be isolated or occupied. Electric-field images were obtained
using a polychromatic, spin-polarized neutron beam with a sensitive polarimetry
scheme. This work may enable new diagnostic power of the structure of electric
potential, electric polarization, charge distribution, and dielectric constant
by imaging spatially dependent electric fields in objects that cannot be
accessed by other conventional probes.
