Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 13 of 13 for “"pump-probe experiment"”.
-
Ultrafast reaction dynamics of polyatomic molecules probed by ionization
… 7-dehydrocholesterol are investigated in a fs pump-probe experiment using ionization as the probe step. Concerning the 1,3,5-cyclooctatriene photoreaction, there are strong arguments for the participation of two different reaction channels (involving a 3-center and a 4-center substructure) …
-
Photoionisation und Photodissoziation von Wasserstoff
… Elektronenbilder aufgenommen <br>werden. <br>In Experimenten mit H2 im starken Laserfeld ( ca. 0.1 TW/cm2) konnten die <br>theoretisch vorhergesagten Effekte Bondsoftening , Above Threshold Dissociation <br>und Coulombexplosion in den Fragmentspektren indentifiziert werden. Die …
-
Study of Wavepacket Dynamics in Rubidium Vapor by Means of Time-Frequency Analysis
… atomic wavepackets are optically detected via a pump-probe experiment based on axially phase-matched parametric four-wave mixing (FWM). This nonlinear process results in coherent ultraviolet (UV) or violet emission that carries information about the relative number densities of the excited …
-
Beobachtung und Steuerung molekularer Dynamik mit Femtosekunden-Laserpulsen
… Nachweis der Photofragmente verwendet. Die Experimente wurden an einigen Spezies der Methylhalogenide CH2XY (X,Y = Halogen) durchgeführt. Diese Verbindungen wurden als Modellsysteme gewählt, da sich gezeigt hat, dass auf Grund stark gekoppelter konkurrierender Dissoziationskanäle durch …
-
Surfactant dynamics at interfaces : a series of second harmonic generation experiments
… In order to assess this model, we designed a SHG pump-probe experiment that addresses the orientation dynamics. Results obtained reveal that the orientation dynamics occur in the picosecond time regime, being in strong contradiction with the two states model. The second model regards the interface …
-
Nanoparticle-nanoparticle interactions and light-matter interaction studied by simulated absorption spectroscopy
… electron and hole excitations in the simulated pump-probe experiment can be distinguished. Because of the nanorod-like shape of Au₃₈, different energies and directions of the pump laser are applied to Au₃₈ to induce absorptions polarized in different directions. This work provides an opportunity …
-
Towards multiple quantum well optically pumped far infrared lasers
Optically pumped lasers based on GaAs/AlGaAs multiple quantum well (MQW) structures are a potential coherent source in the far infrared (FIR) wavelengths. The FIR (~ 30 to 300 µm) is a region within the electromagnetic spectrum that has seen relatively little development. No practical solid-state …
-
Following a Photochemical Reaction of Br2 using Photoion and Photoelectron Momentum Spectroscopy
… discrepancies. At last, we will present our Br2 pump-probe experiment, which encompasses the experimental techniques and results. We employed a cold target recoil ion momentum spectroscopy (COLTRIMS) apparatus to record the momentum spectra of ions and electrons from the ionization of …
-
Dissociation dynamics of diatomic molecules in intense fields
… measured data in collaboration with different experimental groups worldwide. The first three chapters of the thesis cover the introduction and the background on solving time-independent and time-dependent Schrödinger equation. The numerical results in this thesis are presented in four chapters, …
-
Ankunftszeitbestimmung ultrakurzer XUV Pulse von FLASH durch Kreuzkorrelation mit ultrakurzen NIR Pulsen
… an electronically synchronized fs NIR laser, pump-probe experiments can be performed. Currently, the ultimate time resolution given by the pulse duration of both pulses is not achievable due to unpredictable shot-to-shot arrival time fluctuations of the FLASH pulses. The temporal resolution …
-
Exploring electron and phonon transport at the nanoscale for thermoelectric energy conversion
… nanoscale transport using both modeling and experiment. The first portion of the thesis studies how electrons and phonons are affected by grain boundaries in nanocomposite thermoelectric materials, where the grain sizes are smaller than mean free paths (MFPs). We use the Boltzmann transport …
-
Four-Wave Mixing Techniques Applied to the Investigation of Non-Adiabatic Dynamics in Polyatomic Molecules
In the experiments presented in this work, third-order, time-resolved spectroscopy was applied to the disentanglement of nuclear and electronic degrees of freedom in polyatomic molecules. The motivation for approaching this problem was given by the decisive role that the coupling of nuclear and …
-
Optically induced ferro- and antiferromagnetic dynamics in the rare-earth metal dysprosium
… laser pulses in a metal is investigated. The experiments were performed at the FemtoSpex slicing facility at the storage ring BESSY II, an unique source for ultra-short elliptically polarized x-ray pulses. Laser-induced changes of the 4f-magnetic order parameter in ferro- and antiferromagnetic …