Berlin 2014 – wissenschaftliches Programm

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A: Fachverband Atomphysik

A 15: Poster: Interaction with strong or short laser pulses

A 15.5: Poster

Montag, 17. März 2014, 16:30–18:30, Spree-Palais

Coulomb effects in two-color atomic ionization and "the phase of the phase" in the photoelectron yield — •Mohammad Adel Almajid and Dieter Bauer — Institut für Physik, Universität Rostock, 18051 Rostock

The plain strong field approximation (SFA) fails in reproducing ab initio spectra obtained by solving the time-dependent Schrödinger equation (TDSE) exactly. There have been various attempts to include Coulomb effects into the direct SFA, one of them being the Coulomb-Volkov approximation (CVA). In our work, we compare TDSE and CVA-SFA photoelectron spectra, in particular for two-color, colinearly polarized pulses, where the relative phase between the two laser fields affects the photoelectron dynamics. A pronounced disagreement between exact TDSE and CVA-SFA results is found for the so-called direct electrons that move towards the detector without hard rescattering at the parent ion. The rescattered electrons instead are well described already by the SFA, extended for the rescattering matrix element. We analyze the photoelectron spectra by Fourier-transforming the momentum-dependent yield as a function of the relative phase between the two pulses, thus obtaining "the phase of the phase". Plotted vs the momenta parallel and perpendicular to the laser polarization direction, this entity tells how the yield of photoelectrons with a certain final momentum is synchronized with respect to changes of the relative phase.