Inst. Optik und Atomare Physik

163 Items

Recent Submissions
Laboratory based GIXRF and GEXRF spectrometers for multilayer structure investigations

Szwedowski-Rammert, Veronika ; Baumann, Jonas ; Schlesiger, Christopher ; Waldschläger, Ulrich ; Gross, Armin ; Kanngießer, Birgit ; Mantouvalou, Ioanna (2019-02-11)

This work reports laboratory angle resolved measurements with the goal of establishing laboratory techniques to obtain a more complete idea of the intralayer composition of multilayer samples. While X-ray reflectometry is a widely available technique for the characterization of multilayer samples, angle resolved XRF measurements (grazing emission/incidence X-ray fluorescence) are usually perfor...

Effect of alkali ions on optical properties of flavins: vibronic spectra of cryogenic M+lumiflavin complexes (M = Li–Cs)

Müller, David ; Nieto, Pablo ; Miyazaki, Mitsuhiko ; Dopfer, Otto (2019-01-07)

Flavin compounds are frequently used by nature in photochemical processes because of their unique optical properties which can be strongly modulated by the surrounding environment such as solvation or coordination with metal ions. Herein, we employ vibronic photodissociation spectroscopy of cryogenic M+LF complexes composed of lumiflavin (LF, C13H12N4O2), the parent molecule of the flavin famil...

Broadband ultrafast spectroscopy on mixed–dimensional InAs/GaAs systems

Kolarczik, Mirco (2019)

This thesis deals with light matter interaction and electron dynamics in coupled systems of nanostructured III-V semiconductors, particularly with quantum dots embedded in quantum wells. Its focus is on the role of dimensionality and the characterization of quantum dot states with respect to their two- and many-level nature. The sample under investigation is a semiconductor optical amplifier un...

New approaches in angle resolved X-ray analysis of stratified materials in the laboratory

Szwedowski-Rammert, Veronika (2019)

Providing access to angular resolved X-ray fluorescence methods in laboratories can enhance the dissemination of these methods for the depth-resolved elemental analysis of samples with layers in the nanometer range. The measurements are so far mainly performed at synchrotron radiation facilities and thus the number of users is limited. Especially in the hard X-ray range, where the production of...

Megaelectron volt secondary-ion mass spectrometry – yield dependence on experimental parameters and new capabilities of the technique

Stoytschew, Valentin (2019)

Time of flight Mega-electron Secondary Ion Mass Spectroscopy (TOF MeV SIMS) is a mass spectrometry technique using swift heavy ions (𝑚>16 𝑢, 𝐸𝑘𝑖𝑛>1 𝑀𝑒𝑉) to induce desorption of secondary ions from a sample. While swift heavy ions have been used for several decades to achieve high molecular secondary ion yields in mass spectrometry, there has been no systematic investigation into the ex...

Non-linear x-ray diffraction from ferromagnetic thin-films

Schneider, Michael (2019)

In this thesis, fluence-dependent absorption and diffraction from solid-state samples in the extreme ultra-violet (XUV) regime is investigated. At these wavelengths, fluence dependent effects occur predominantly in experiments at free-electron laser (FEL) sources and attract considerable interest as they have important implications for the conclusiveness of studies performed at these light sour...

Microhydration of protonated 5-hydroxyindole revealed by infrared spectroscopy

Klyne, Johanna ; Dopfer, Otto (2019-01-08)

Controlled microsolvation of protonated aromatic biomolecules with water is fundamental to understand proton transfer reactions in aqueous environments. We measured infrared photodissociation (IRPD) spectra of mass-selected microhydrates of protonated 5-hydroxyindole (5HIH+–Wn, W = H2O, n = 1–3) in the OH and NH stretch ranges (2700–3800 cm−1), which are sensitive to the spectroscopic character...

A comparative study demonstrates strong size tunability of carrier–phonon coupling in CdSe-based 2D and 0D nanocrystals

Scott, Riccardo ; Prudnikau, Anatol V. ; Antanovich, Artsiom ; Christodoulou, Sotirios ; Riedl, Thomas ; Bertrand, Guillaume H. V. ; Owschimikow, Nina ; Lindner, Jörg K. N. ; Hens, Zeger ; Moreels, Iwan ; Artemyev, Mikhail ; Woggon, Ulrike ; Achtstein, Alexander W. (2019-01-30)

In a comparative study we investigate the carrier–phonon coupling in CdSe based core-only and hetero 2D as well as 0D nanoparticles. We demonstrate that the coupling can be strongly tuned by the lateral size of nanoplatelets, while, due to the weak lateral confinement, the transition energies are only altered by tens of meV. Our analysis shows that an increase in the lateral platelet area resul...

Spectroscopy of protonated aromatic and chiral biomolecules

Klyne, Johanna Karin (2019)

Characterizing the interactions in clusters of protonated aromatic and chiral biomolecules is essential to understand their chemical reactions and molecular recognition. In this thesis, three prototypical biomolecular building blocks are investigated by sophisticated infrared (IR) and ultraviolet (UV) laser spectroscopic methods and density functional theory (DFT) calculations. First, the proto...

Röntgenabsorptionsspektroskopie im Labor

Schlesiger, Christopher Philip (2019)

In der vorliegenden Arbeit wird ein flexibler Laboraufbau für Röntgenabsorptionsspektroskopie vorgestellt, mit dem es möglich, ist verdünnte Proben mit hoher Effizienz zu messen und zu charakterisieren. Das Ziel ist, durch diesen Aufbau den möglichen Anwenderkreis aufgrund der höheren Verfügbarkeit einer Labormethode, im Gegensatz zur üblichen Verwendung ausschließlich an Synchrotronstrahlungsq...

Simulation of building blocks for silicon photonic integrated circuits

Atif, Muhammad (2019)

This study focusses upon simulation of building blocks for silicon photonic integrated circuits. The two necessary steps for the simulation are control of temperature in the integrated Mach-Zehnder Interferometer (MZI) or modulators (MZM), and stabilization and tuning of optical modulated spectrum in node-matched-diode (NMD) Fabry-Pérot (FP) resonator or modulators. Hence the thesis consists of...

Quantification of silver nanoparticle uptake and distribution within individual human macrophages by FIB/SEM slice and view

Gührs, Erik ; Schneider, Michael ; Günther, Christian M. ; Hessing, Piet ; Heitz, Karen ; Wittke, Doreen ; Oliver, Ana López-Serrano ; Jakubowski, Norbert ; Plendl, Johanna ; Eisebitt, Stefan ; Haase, Andrea (2017-03-21)

Background Quantification of nanoparticle (NP) uptake in cells or tissues is very important for safety assessment. Often, electron microscopy based approaches are used for this purpose, which allow imaging at very high resolution. However, precise quantification of NP numbers in cells and tissues remains challenging. The aim of this study was to present a novel approach, that combines precise ...

In situ scanning electron microscopy studies on the dynamics of metal-catalyzed CVD growth of graphene

Wang, Zhu-Jun (2017)

Electron microscopy has contributed tremendously to our understanding of catalysis. Scanning- and transmission electron microscopes are used to investigate the structure and composition of catalytically active materials. They provide guiding feedback during synthesis of catalyst precursors and are used to study reaction induced modifications on spent catalysts. Electron microscopy delivers loca...

Terahertz quantum-cascade lasers for spectroscopic applications

Röben, Benjamin Malte (2018)

Terahertz (THz) quantum-cascade lasers (QCLs) are unipolar semiconductor heterostructure lasers that emit in the far-infrared spectral range. They are very attractive radiation sources for spectroscopy, since they are very compact and exhibit typical output powers of severalmWas well as linewidths in the MHz to kHz range. This thesis presents the development of methods to tailor the emission ch...

Magnetische und elektronische Eigenschaften von Übergangsmetallkomplexen in der Gasphase

Bülow, Christine (2018)

In dieser Arbeit wurde der Übergang von einem Hochspin- zu einem Niedrigspinzustand in verschiedenen Systemen mit jeweils einem Übergangsmetallatom mittels Röntgenabsorptions- und XMCD-Spektroskopie in der Gasphase untersucht. Im Vordergrund steht die Frage wie dieser magnetische Übergang von der Anzahl der 3d Elektronen, der Struktur und den Liganden abhängt. Dabei wird von in einem früheren P...

Spektroskopie der Neurotransmitter Tryptamin und Phenylethylamin

Schütz, Markus (2018)

The maintenance of bodily functions in living beings is determined by a variety of biochemical processes, collectively referred to as metabolism. Molecular spectroscopy can be used to study processes at the molecular level and to draw conclusions about interactions and possible functionalities. The signal transmission between chemical neurons is based inter alia on the binding of a neurotransmi...

Jitter-correction for IR/UV-XUV pump-probe experiments at the FLASH free-electron laser

Savelyev, Evgeny ; Boll, Rebecca ; Bomme, Cédric ; Schirmel, Nora ; Redlin, Harald ; Erk, Benjamin ; Düsterer, Stefan ; Müller, Erland ; Höppner, Hauke ; Toleikis, Sven ; Müller, Jost ; Kristin Czwalinna, Marie ; Treusch, Rolf ; Kierspel, Thomas ; Mullins, Terence ; Trippel, Sebastian ; Wiese, Joss ; Küpper, Jochen ; Brauβe, Felix ; Krecinic, Faruk ; Rouzée, Arnaud ; Rudawski, Piotr ; Johnsson, Per ; Amini, Kasra ; Lauer, Alexandra ; Burt, Michael ; Brouard, Mark ; Christensen, Lauge ; Thøgersen, Jan ; Stapelfeldt, Henrik ; Berrah, Nora ; Müller, Maria ; Ulmer, Anatoli ; Techert, Simone ; Rudenko, Artem ; Rolles, Daniel (2017)

In pump-probe experiments employing a free-electron laser (FEL) in combination with a synchronized optical femtosecond laser, the arrival-time jitter between the FEL pulse and the optical laser pulse often severely limits the temporal resolution that can be achieved. Here, we present a pump-probe experiment on the UV-induced dissociation of 2,6-difluoroiodobenzene (C6H3F2I) molecules performed ...

Spektroskopie an silizium- und kohlenstoffhaltigen Clustern: Dotierung und Hybride

Savoca, Marco (2018)

Silicon oxides and silicon carbides are not only in the focus of the semiconductor industry and relevant for the development of new materials from clusters and nanoparticles, they are also of interest in the chemistry of the interstellar medium. In this context, the availability of experimental data regarding structure of doped silicon clusters is an essential basis for exploring and controllin...

Off-Axis Electron Holographic Focal Series of GaN

Niermann, Tore (2014)

This is a high resolution off-axis electron hologram series obtained with a transmission electron microscope of a Gallium Nitride (GaN) crystal in <11-20> zoneaxis orientation at atomic resolution. It contains the raw data of two holographic focal series obtained under equal conditions (no strong changes in illumination or microscope setup) a few minutes apart. The first series is a focal serie...

Ultrafast dynamics of nanoparticles in highly intense X-Ray pulses

Bucher, Maximilian Jakob (2017)

With the advent of X-ray free electron laser, such as the Linac Coherent Light Source (LCLS), structural studies on non-repetitive and non-reproducible nanoparticles, such as single bio-molecules appear imminent. A key challenge to increasing the resolution of single particle imaging is radiation damage. Only a sound understanding of the underlying damage processes, such as the nanoplasma expan...