Berlin 2001 – wissenschaftliches Programm

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A: Atomphysik

A 3: Multi Photon Processes

A 3.3: Vortrag

Montag, 2. April 2001, 16:15–16:30, H1058

Photodetachment of Negative Ions in Strong Laserfields — •Rainer Reichle, Igor Yu. Kiyan, and Hanspeter Helm — Fak. f. Physik, Univ. Freiburg, Hermann-Herder-Str. 3, 79104 Freiburg

We present an experiment that allows direct imaging of the momentum distribution of electrons, formed in a keV atomic beam after interaction with a short, intense laser pulse. This permits a straightforward visualization of the electron momentum distribution on a 2D position-sensitive detector after photodetachment of negative ions. Our special design avoids imaging distortions caused by a finite ion beam width as well as it eliminates kinematic motional effects of the target ions. As in neutral atoms, in negative ions exposed to strong laser fields, nonlinear effects like tunnel ionisation, multiphoton processes, and excess photon detachment (EPD) occur. We observe nonresonant EPD processes in H⁻ involving at least three excess photons. For negative ions, analytical, Keldysh-like theoretical models exist [1], which are valid over a wide range of laser intensities and frequencies. Quantitative comparisons of our experiment with these theories will be given.
Supported by DFG (SFB 276, TP C14)

[1] G. F. Gribakin, M. Yu. Kuchiev, Phys. Rev. A 55, 3760 (1997)