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If we set up a double slit experiment, where at the slits we put a strong magnetic/electric field, and sent an electron through, what would happen? Would the magnetic/electric field collapse the wave function of the electron, or would the electron still create an interference pattern?

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    $\begingroup$ Why would the fields collapse the wave function? You would have to account for their effect on the electron propagation, sure, but that is all. You can certainly perform electron diffraction on magnetic materials for example. $\endgroup$ – Jon Custer Mar 31 '17 at 19:57
  • $\begingroup$ The electrons already deal with a strong electric field ... when they pass close to the electrons of the atoms in the "wall" of the slit. $\endgroup$ – David White Mar 31 '17 at 22:54
  • $\begingroup$ @DavidWhite Interesting comment because it takes in account that there is an interaction with the surface electrons at all. looking on the explanations for interference behind slits this point is not taken in account. I´ve published an answer to show how it is influenced. ANd if this is valid for electrons why it is not valid for photons? See physics.stackexchange.com/questions/158105/… $\endgroup$ – HolgerFiedler Apr 2 '17 at 6:44
  • $\begingroup$ @HolgerFiedler, since photons obviously can interact with electrons, my opinion is that photons are influenced by their interaction with electrons. $\endgroup$ – David White Apr 2 '17 at 18:25
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If we set up a double slit experiment, where at the slits we put a strong magnetic/electric field, and sent an electron through, what would happen?

Experiments with electrons on edges under the influence of an electric field were done in 1956 by G. Möllenstedt and H. Düker. ("Beobachtungen und Messungen an Biprisma-lnterferenzen mit Elektronenwellen" (Observations and measurements on biprism interferences with electron waves) from Zeitschrift für Naturforschung 10 a S. 256a). For deeper reading an excerpt of mine in poor English.

enter image description here The two researchers from the Institute of Experimental and Applied Physics of the University of Tübingen directed an electron beam from a dot-shaped source through an electrostatic biprism. The biprism consisted of a gold coated quartz wire from two micrometers thickness (F), which was stretched between the two grounded plates of a plate capacitor.

If initially the biprism stays potential free, the entrance slit produces a shadow of the wire and outside the geometric shadow appear electron-free fringes, called according to the original script "FRESNEL diffraction fringes".

enter image description here

Applying a positive voltage of only a few volts on the filamentary center plate, the electrons of the two partial beams are bent towards the center. For the - in accordiance to light 105 times smaller cross section of the electron - a potential of +7 volts was enough for a successfully diffraction of electrons. "The wire potential was increased in small increments from zero to + 7V. The small filament diameter from a few μ causes that the required for the beam deflection field strength is achieved in the vicinity of the wire after just a few volts potential difference"(p. 384). With a positive potential the diffraction images of the right and left edges are shifted to each other.

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Would the magnetic/electric field collapse the wave function of the electron, or would the electron still create an interference pattern?

As you see above, no. The intensity distribution behind slits (as well as behind any sharp or thin edges) stil appears. And the dimensions of the fringes are influenced by the applied electric potential.

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