Darmstadt 2008 – scientific programme

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A: Fachverband Atomphysik

A 12: Posters: Interaction with intense laser pulses

A 12.3: Poster

Tuesday, March 11, 2008, 16:30–18:30, Poster C3

Photoelectron imaging spectroscopy of potassium atoms with polarization-shaped fs-laser pulses — •Marc Krug, Jens Köhler, Matthias Wollenhaupt, and Thomas Baumert — Universität Kassel, Institut für Physik und Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), Heinrich-Plett-Str. 40, D-34132 Kassel, Germany

We present our new approach to use a photoelectron imaging spectrometer to measure two-dimensional projections of three-dimensional electron wave packets resulting from excitation of potassium atoms by polarization-shaped laser pulses. This resonant multi-photon ionization is very sensitive to the helicity of the used laser light and leads to different shapes of the outgoing electron wave packet. As a test experiment, we use an achromatic half-wave plate to rotate the polarization axis of the laser pulse and analyze the measured photoelectron distributions in a tomography-like way. Additionally a quarter-wave plate is used to create circularly polarized laser pulses. This strong-field excitation was recently discussed in terms of electric ring currents in atoms. We also make use of a Fourier transform polarization shaper which provides full control over the ellipticity of all spectral components in the pulse and measure angle-resolved photoelectron spectra of the shaped laser pulses. In the special cases of linearly and circularly polarized light excellent agreement between the two approaches is shown. However, employment of the pulse shaper opens up versatile possibilities to exert control on the atomic excitation by specifically designed laser pulses.