Berlin 2001 – wissenschaftliches Programm

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A: Atomphysik

A 3: Multi Photon Processes

A 3.11: Vortrag

Montag, 2. April 2001, 18:15–18:30, H1058

Ionization in intense laser fields – an ideal example for Feynman’s path integral — •Gerhard G. Paulus, Felix Grasbon, and Herbert Walther — MPI für Quantenoptik, D-85748 Garching

In order to describe the interaction of atoms with intense laser fields analytically, Keldysh-type theories are used. It is possible to rewrite these theories such that the transition amplitude is a sum of saddle points of Feynman path integrals. The real parts of the saddle points are closely related to classical electron trajectories. Therefore, we adopt the notation that the transition amplitude for ionization is the sum of a few “quantum trajectories” [1].

We performed experiments where the experimental situation was adjusted such that only one pair of quantum trajectories contributes to a given energy interval of the photoelectron energy spectrum. Thus, by specifying the electron’s energy, it is possible to determine on which quantum trajectory the electron left the atom. In fact, by inspection of the real part of this trajectory an intuitive understanding of the spectrum can be obtained. In addition to this, we present measurements in which interference effects of the quantum trajectories become observable.

[1] R. Kopold et al., Phys. Rev. Lett. 84, 3831 (2000)