Generation of Attosecond Pulses in Atoms and Molecules

Abstract : In several experiments, we demonstrate the potential of the process of high-order harmonic generation for observing ultrafast intra-molecular electron and nuclear dynamics. The largest part of this thesis treats experiments where molecules constitute the generating medium and the recolliding electron wavepacket takes the role of a 'self-probe'. Measurements of phase and amplitude of the harmonic emission from CO2 and N2 molecules aligned in the laboratory frame allow us to extract the recombination dipole matrix element. The latter contains the signature of quantum interference between the free and bound parts of the total electronic wavefunction. The utilization of this interference for the shaping of the attosecond (1as=10−18s) XUV emission is demonstrated. Furthermore, we study theoretically molecular orbital tomography from the recombination dipole matrix elements and demonstrate its experimental feasibility. This opens the perspective of imaging ultrafast distortions of a frontier orbital during a chemical reaction. In a second part of this thesis, we use the coherent XUV light emitted by argon atoms to photoionize N2 molecules and measure how an auto-ionizing resonance modifies the spectral phase of the ejected photoelectron wavepacket. The last chapter of this thesis describes studies of the generation of XUV attosecond pulses in a different medium: ablation plasmas. The first temporal characterization of such a source demonstrates its femtosecond and attosecond structure.
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Submitted on : Monday, July 16, 2012 - 1:54:06 PM
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  • HAL Id : tel-00440190, version 2

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Stefan Haessler. Generation of Attosecond Pulses in Atoms and Molecules. Atomic Physics [physics.atom-ph]. Université Paris Sud - Paris XI, 2009. English. ⟨tel-00440190v2⟩

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