A gas of Rb atoms in a static electric field has been photoexcited to just above the classical ionization threshold by a phase-locked sequence of two far infrared pulses. A single laser pulse generates a series of ejected electron packets emerging at the saddle point of the potential; each of the ejected packets is characterized by a phase and a chirp. We calculate and measure these phases and chirps using the time dependent interference of the electronic wave function controlled by the delay between the two light pulses.

Phys. Rev. Lett.

Rella, C. W., Texier, F., Noordam, L. D., & Robicheaux, F. (2000). Relative phase measurement of a Stark wave packet in the vicinity of the saddle point. Phys.Rev.Lett., 85, 4233–4236.