Has the ballistic motion of an electron in gravitational field ever been measured? Reading this question I thought of an argument that an electron's trajectory would bend in the gravitational field despite the electron's being incapable of strong interaction; this would then disprove the conjecture stated in that question. But then I couldn't find any references to actual experiments that have been done to measure this ballistic motion of an electron in gravitational field.
Has such motion actually been measured?
 A: After searching online for a while, I found this paper, entitled "EXPERIMENTAL COMPARISON OF THE GRAVITATIONAL FORCE ON FREELY FALLING ELECTRONS AND METALLIC ELECTRONS". The paper refers to two earlier papers:
1.F.C.Witteborn, L.V.Knight,and W.M. Fairbank, in Proceedings of the Ninth International Conference on Low Temperature Physics, edited by J.G.Daunt, D.0. Edwards, F.J. Milford, and M. Yaqub {Plenum Press, New York, 1965), p.1248.


*F.C.Witteborn, thesis, Stanford University, 1965 (unpublished).

There are a bunch of related papers here.
Bottom line: it appears that measurements have been done.
A: EDIT: see the answer by S. McGrew. Turns out there's some clever methods of releasing extremely low energy free electrons, which makes gravitational effects just measureable.
Let's think about the size of the effect you're looking for.
Suppose you sputter off an electron with a very low energy of around 1 eV. This corresponds to an electron velocity of about 600 km/s. If you set up a vacuum chamber 1 km long, the electron travels across it in around 1.5 ms. In that time, gravity on Earth's surface will have deflected it by under 30 microns - 0.03 mm! Actual electron emissions are much higher energy, especially for long-chamber situations - most particle accelerators operate with energies in the MeV range, which gives deflections a thousand times less. More or less, this is completely impractical to measure, since this will be many orders of magnitude smaller than your beam width.
