Number 335 (Story #2), September 5, 1997 by Phillip F. Schewe and Ben Stein|
VIEWING NANOSCOPIC ELECTROMAGNETIC FIELDS IN REAL TIME is now possible. Conventional electron holography techniques must first capture an image of an electromagnetic field, then reconstruct it in a second step. Researchers in Japan (Tsukasa Hirayama, Japan Fine Ceramics Center, KYN00252@niftyserve.or.jp) pass an electron beam through the electromagnetic field of interest (typically emanating from a small object) and combine it with a pair of reference beams to record a "three-wave interference" pattern onto a film or CCD camera. Whereas conventional textbooks often depict electric and magnetic fields as "lines of force" (for example, the electric field from a point charge such as an electron has straight lines emanating in all directions from the particle), the three-wave interference pattern yields the "equipotential lines" which are perpendicular to the lines of force. The technique can image electromagnetic fields with features in the tens of nanometers. Applying their technique to an electrically charged latex particle (0.5 microns in diameter), the researchers deduced that the imaged electric field was created by approximately 400 electrons in the particle. (Journal of Applied Physics, 15 July 1997; images at Physics News Graphics).