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Spectroscopie de phase multi-dimensionnelle de l'émission attoseconde moléculaire

Abstract : A molecule subjected to intense laser field infra-red (in the range of October 14 W.cm-2) can be ionized by the tunnel effect. The electronic wave packet (POE) thus liberated is then accelerated by the laser field and, when switching back to the vicinity of the parent ion, it has a certain probability to recombine into its ground state. During this recombination, the POE releases its energy in the form of a flash Attoseconds (1as = 10 -18s) of XUV radiation. This coherent emission is produced at each laser half cycle resulting in a pulse train attosecond. In the spectral domain, this process corresponds to a discrete spectrum of harmonics of the laser frequency. The recombination step of the electron with the parent ion can be considered as a probe of the molecular structure of generation valence orbitals involved in the harmonics and the dynamic occurring in the ion during the excursion of the electron in the continuum. By characterizing amplitude, phase and polarization, harmonic emission associated with this recombination, it is possible to trace the structural and dynamic information with an accuracy of the order of the Ångström and attosecond resolution. In particular, the phase of the harmonic emission is difficult to characterize encodes information essential to the proper understanding of the processes taking place in the build environment. We present the principles and test new techniques allows both characterize the phase Attoseconds emission along several dimensions simultaneously and in an optimized time. In the first part, we present a method to rapidly characterize the spectral phase of the harmonic emission based on a model of the strong field photoionization two colors (RABBIT). We then introduce a new interferometer with two sources, to measure the emission of attosecond phase variations induced by the excitation of a vibrational or rotational wave packet. This very stable device, compact and simple energy based on the use of a diffractive optical element (DOE) binary. After describing our device by digital simulations and preliminary experiments, we show that it is so sensitive that it can measure the phase variations depending on the excitation parameter for different electron trajectories in the continuum. For nitrogen and carbon dioxide, experimental measurements show very different phase changes for the first two electron trajectories. This DOE is then used to measure the phase of the harmonic emission in the molecules aligned in the same experimental conditions as the RABBIT. Both experiments successively give consistent results we combine two different methods: HUNTER and MAMMOTH. Finally, we propose to combine the DOE with a transient network to simultaneously characterize the molecular phase of the attosecond emission in two different polarization axes. These different techniques of phase measurement allowed us to accurately study the following harmonic emission different dimensions (alignment angle, generating intensity electronic trajectory) and derive new information on the generation mechanism in molecules .
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https://tel.archives-ouvertes.fr/tel-01100464
Contributor : Antoine Camper <>
Submitted on : Friday, January 9, 2015 - 1:27:03 PM
Last modification on : Monday, December 14, 2020 - 5:20:39 PM
Long-term archiving on: : Friday, April 10, 2015 - 10:16:25 AM

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  • HAL Id : tel-01100464, version 1

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Antoine Camper. Spectroscopie de phase multi-dimensionnelle de l'émission attoseconde moléculaire. Physique [physics]. Université Paris XI, 2014. Français. ⟨NNT : 10014205⟩. ⟨tel-01100464v1⟩

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