Personal web page : http://iramis.cea.fr/Pisp/pascal.salieres/
Laboratory link : http://iramis.cea.fr/LIDYL/atto/
More : http://attolab.fr/
The student will first generate XUV attosecond pulses using an intense Titanium:Sapphire laser (ATTOLab Excellence Equipment), and then use them to investigate the ionization dynamics of molecular gases: electron ejection, electronic rearrangements in the ion, charge migration, quantum decoherence…
Detailed summary :
Recently, the generation of sub-femtosecond pulses, so-called attosecond pulses (1 as=10-18 s), has made impressive progress. These ultrashort pulses open new perspectives for the exploration of matter at unprecedented timescale. Their generation result from the strong nonlinear interaction of short intense infrared (IR) laser pulses (~20 femtoseconds) with atomic or molecular gases. High order harmonics of the fundamental frequency are produced, covering a large spectral bandwidth in the extreme ultraviolet (XUV) range. In the temporal domain, this coherent radiation forms a train of 100 attosecond pulses . In order to generate isolated pulses, it is necessary to confine the generation in an ultrashort temporal window, which implies the development of various optical confinement techniques.
With such attosecond pulses, it becomes possible to investigate the fastest dynamics in matter, i.e., electronic dynamics that occur naturally on this timescale. Attosecond spectroscopy thus allows studying fundamental processes such as photo-ionization, in order to answer questions such as: how long does it take to remove one electron from an atom or a molecule? The measurement of such tiny ionization delays is currently a “hot topic” in the scientific community. In particular, the study of the ionization dynamics close to resonances gives access to detailed information on the atomic/molecular structure, such as the electronic rearrangements in the remaining ion upon electron ejection .
The objective of the thesis is first to generate attosecond pulses with duration and central frequency adequate for the excitation of various molecular systems. The objective is then to measure the instant of appearance and the angular distribution of the charged particles, electrons and ions. These spatial and temporal informations will allow the reconstruction of the full 3D movie of the electron ejection, as well as of the hole migration in the ion leading to fragmentation. Finally, quantum decoherence, e.g., induced by ion-photoelectron entanglement, will be studied using a new technique recently demonstrated in our laboratory .
The experimental work will include the development and operation of a setup installed on the FAB1 laser of the ATTOLab Excellence Equipment allowing: i) the generation of attosecond XUV radiation, ii) its characterization using quantum interferometry, iii) its use in photo-ionization spectroscopy. The theoretical aspects will also be developed. The student will be trained in ultrafast optics, atomic and molecular physics, quantum chemistry, and will acquire a good mastery of charged particle spectrometry. A background in ultrafast optics, nonlinear optics, atomic and molecular physics is required.
Part of this work will be performed in collaboration with partner French and European laboratories through joint experiments in the different associated laboratories (Milano, Lund).
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