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.

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Journal 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.