Zielinski, Alejandro (2016): Fully differential photoelectron spectra of hydrogen and helium atoms. Dissertation, LMU München: Fakultät für Physik 

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Abstract
The ability to probe and manipulate electron dynamics and correlations on their characteristic time scales would open up many technological and scientific possibilities. While modern laser technology already allows to do that in principle, a lot of theoretical ground work is still missing. This thesis focuses on the elementary effect of laser strong field ionization of the two simplest systems: The Hydrogen and Helium atoms. To that end, the timedependent Schroedinger equation is solved numerically, and photoelectron spectra are extracted using the highly efficient tSurff technique. We implemented both the one and two particle versions of tSurff together with several other numerical techniques in a new parallelizable C++ code. We provide details on the employed methods and algorithms, and study numerical efficiency properties of various approaches. We propose a description of the electric field interaction in a mixture of length and velocity gauge for the correct and most efficient implementation of a coupled channels approach, which can be used to compute accurate single ionization photoelectron spectra from true multielectron systems, even molecules. We provide extensive numerical data for a detailed study of the Hydrogen atom in an Attoclock experimental setup, where it is found that the involved strong field tunnel ionization processes can be considered instantaneous. In particular, there appear no tunneling delays, which can be used as a calibration for experiments with more complicated targets. Similarly, it is investigated whether discrepancies between theory and experimental data for the longitudinal photoelectron momentum spread, resulting from photoionization of Helium in elliptically polarized laser pulses, can be explained by nonadiabatic effects, and a related consistency problem in current laser intensity calibration methods is pointed out. We further show that Fano resonance line shapes of doubly excited states in the Helium atom, prominently appearing in single ionization spectra generated by short wavelength laser pulses, can be controlled by an external long wavelength streaking field. The resulting line shapes are still characterized by the general Fano situation, but with a complex  rather than real  Fano parameter. We provide a theoretical description of this two color process and prove numerically that the entire doubly excited state series exhibits synchronized line shape modifications as the specifics of the involved states are unimportant. Finally, we compute fully differential double ionization spectra and suggest a measure of correlation that is directly applicable to experimental data. We confirm literature results at short wavelengths, and achieve to compute fivefold differential double ionization photoelectron spectra at infrared wavelengths from the Helium atom, thereby reproducing a characteristic several orders of magnitude enhancement of double emission due to correlation effects.
Dokumententyp:  Dissertation (Dissertation, LMU München) 

Keywords:  Quantum Mechanics, Attosecond Physics 
Themengebiete:  500 Naturwissenschaften und Mathematik
500 Naturwissenschaften und Mathematik > 530 Physik 
Fakultäten:  Fakultät für Physik 
Sprache der Dissertation:  Englisch 
Datum der mündlichen Prüfung:  26. Januar 2016 
1. Berichterstatter/in:  Scrinzi, Armin 
URN des Dokumentes:  urn:nbn:de:bvb:19191104 
MD5 Prüfsumme der PDFDatei:  e93b150c2d2788276dc5a2b80231fdff 
Signatur der gedruckten Ausgabe:  0001/UMC 23552 
ID Code:  19110 
Eingestellt am:  11. Feb. 2016 09:56 
Letzte Änderungen:  11. Feb. 2016 09:56 