A THz "half-cycle" pulse is a fast (<1 ps) unipolar pulse, followed by a slow unipolar pulse of opposite polarity. We found that the interaction of such THz pulses with very high Rydberg states results in a displacement of the electron within the atom, while the ionization is strongly suppressed. In classical terms: the first fast unipolar feature corresponds to a start kick of the Rydberg electron, while the second unipolar feature acts as a stop kick. A semiclassical model is presented which qualitatively reproduces the ionization suppression and redistribution.

Phys. Rev. Lett.

Wesdorp, C., Robicheaux, F., & Noordam, L. D. (2001). Displacing Rydberg electrons: The mono-cycle nature of half-cycle pulses. Phys.Rev.Lett., 87(Article number: 83001), 1–4.