Yes, from the diagram it looks as though, in a vacuum, any escaping charges would rapidly return to de-polarize components of the device, neutralizing the motivating "force". There must be some work done to either oscillate the device or otherwise re-polarize it.
However, the notion of constraining electron motion in two dimensions (say x,y) giving rise to large oscillatory velocities in a z direction seems plausible.... but the z direction is oscillatory and constitutes an "orbital"... at least from these weary eyes.
Longview
