Optical emission from the interaction of fast electrons with metallic films containing a circular aperture: a study of radiative decoherence of fast electrons.

Light emission resulting from the interaction of swift electrons with a distant material is shown to produce an unexpectedly large fraction of decoherence in the moving charges. The decoherence probability diverges for an electron passing through a hole drilled in a perfectly conducting metal film, regardless of the size of the opening. This divergence, which is logarithmic in the ratio of film radius to aperture radius, originates in an infrared catastrophe that differs from other sources of decoherence (e.g., bremsstrahlung radiation). Our results provide new avenues for controlling and assessing the role of coherence during electron acceleration (for example, in transmission electron microscopes) and for exploiting partial quantum interference of fast electrons.