TY  - THES
AU  - Karamatskos, Evangelos Thomas
TI  - Molecular-Frame Angularly-Resolved Photoelectron Spectroscopy
PB  - Universität Hamburg
VL  - Dissertation
CY  - Hamburg
M1  - PUBDB-2019-04144
SP  - 1-196
PY  - 2019
N1  - please upload the teaser image
N1  - Dissertation, Universität Hamburg, 2019
AB  - One of the big technical and scientific challenges today is to accomplish the ultimate dreamof filming chemical reactions with atomic spatial and temporal resolution and recording themolecular movie. Important prerequisites toward this goal are, on the one hand, methodsto create cold, controlled molecular samples and, on the other hand, imaging techniquesthat combine the required spatial and temporal resolution. In recent years, especially due tothe fast progress in the development of laser and electron sources, more and more refinedimaging techniques have become accessible. The combination of quantum state selectionwith laser-induced field-free alignment and orientation, allow to precisely control and preparethe molecules under study, before being imaged. Using ultrafast, high-intensity laser sourcesin the mid-infrared spectral range, self-imaging methods, such as laser-induced electrondiffraction (LIED), have emerged and their full potential can be explored today to image thestructure and dynamics of molecules with atomic spatio-temporal resolution.This work can be divided into two major parts, the control and the imaging part.In the control part, the focus lies on the optimization of field-free alignment using tailoredlight fields. Strong field-free alignment will be presented for three different molecules, rangingfrom the relatively simple linear molecule carbonyl sulfide (OCS) up to the complex asymmetrictop rotor indole, which lacks rotational symmetries and marker atoms. Different experimentaland numerical schemes of increasing complexity will be presented, depending on the complexityof the molecule under study, that allow to achieve strong field-free alignment and to accessthe molecule-fixed frame (MFF).In the imaging part, the LIED method will be employed to image and to retrieve thestatic structure of molecules with atomic resolution, applied on the example of OCS. Theunprecedented degree of field-free alignment of OCS, achieved in the control part, is employedto record angularly-resolved photoelectron momentum distributions (PEMDs) for differentrotational wavepackets and for different orientations of the molecular axis with respectto the ionizing laser polarization. These molecular-frame angularly-resolved photoelectronspectra (MF-ARPES) exhibit large differences, indicating a dependence of the emitted electroncontinuum wavepacket and its dynamics on the shape of the highest occupied molecular orbital(HOMO). In the low-energy region of the PEMDs, strong-field photoelectron holography(SFPH) is observed, revealing diverse interference patterns for different molecular orientations.Moreover, measurements of angle-dependent ionization yields of direct, low-energy electronsand of rescattered, high-energy electrons will be presented, showing clear alignment-dependentfeatures. From these aforementioned observations, conclusions will be drawn about the impactof the underlying molecular orbital on strong-field ionization and field-driven recollisions.
LB  - PUB:(DE-HGF)11
DO  - DOI:10.3204/PUBDB-2019-04144
UR  - https://bib-pubdb1.desy.de/record/427703
ER  -