@phdthesis{Marquetand2007, author = {Marquetand, Philipp}, title = {Vectorial properties and laser control of molecular dynamics}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-24697}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2007}, abstract = {In this work, the laser control of molecules was investigated theoretically. In doing so, emphasis was layed on entering vectorial properties and in particular the orientation in the laboratory frame. Therefore, the rotational degree of freedom had to be included in the quantum mechanical description. The coupled vibrational and rotational dynamics was examined, which is usually not done in coherent control theory. Local control theory was applied, where the field is determined from the dynamics of a system, which reacts with an instantaneous response to the perturbation and, in turn, determines the field again. Thus, the field is entangled with the quantum mechanical motion and the presented examples document, that this leads to an intuitive interpretation of the fields in terms of the underlying molecular dynamics. The limiting case of a classical treatment was shown to give similar results and hence, eases to understand the complicated structure of the control fields. In a different approach, the phase- and amplitude shaping of laser fields was systematically studied in the context of controlling population transfer in molecules.}, subject = {Laserchemie}, language = {en} } @phdthesis{Schneider2009, author = {Schneider, Michael}, title = {Elektronische Spektroskopie und Photodissoziationsverhalten von heterocyclischen Biomolek{\"u}len}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-42190}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2009}, abstract = {Das Photodissoziationsverhalten der Pyrimidinbasen Thymin, Uracil und 5-Methylcytosin wurde mittels Photofragment-Dopplerspektroskopie und Photofragment-Imaging untersucht. Die Photodissoziation erfolgt in allen F{\"a}llen in einem statistischen Prozess nach Mehrphotonenabsorption. Von Purin wurde ebenfalls die Photodissoziation untersucht sowie das elektronische Spektrum des niedrigsten n-pi*-Zustands mittels Photofragment-Anregungsspektroskopie und [1+1']-REMPI-Spektroskopie gemessen. Purin zeigt bei den untersuchten Wellenl{\"a}ngen dasselbe Verhalten wie die Pyrimidinbasen. Das Elektronische Spektrum von Purin zeigt {\"u}ber einen Bereich von {\"u}ber 2000 cm^-1 vom Bandenursprung gut strukturierte Banden, von denen die meisten oberhalb 850 cm^-1 als Kombinationsbanden identifiziert wurden.}, subject = {Photodissoziation}, language = {de} } @phdthesis{Schleier2021, author = {Schleier, Domenik}, title = {Using Photoionization to Investigate Reactive Boron Species and the Kinetics of Hydrocarbon Radicals}, doi = {10.25972/OPUS-24213}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-242137}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2021}, abstract = {This thesis highlights the importance of isomer-selective approaches for the complete analysis of chemical processes. The method of choice is photoelectron/photoion coincidence spectroscopy, which allows simultaneous detection of electrons and ions coming from a single ionization event. Ionization techniques are sensitive and can record multiple species simultaneously, rendering them ideal tools to probe molecular transformations. Coupling these setups to synchrotron radiation allows one to analyze complex mixtures with isomer selectivity, based on ionization energies and vibrational structure in the cation, without any prior separation steps. Only few setups exist that can be used to gather these data, although their impact and applicability is growing steadily in various fields. For closed-shell species an easier and more widely used method is gas-chromatography, but most open shell species would not survive the separation process. Due to the reactivity of radicals they have to be created by selectively converting stable precursor molecules. Depending on the radical generation method different properties can be investigated ranging from thermodynamic data, over concentrations in high temperature environments, to chemical kinetics. The first part of this thesis deals with the determination of bimolecular rate constants. Isomeric hydrocarbon radicals were generated by a high intense UV light pulses and their kinetics with oxygen was measured. The pressure dependence of different isomers in the falloff region was compared to theoretical models, and their reactivity could be explained. The second part deals with boron containing compounds in various electronic situations. The corresponding precursors were successfully synthesized or could be bought. They were subjected to fluorine atoms in chemical reactors or destroyed pyrolytically at high temperatures. Most investigated species exhibited vibronic effects that could be elucidated using high level computations.}, subject = {Biradikal}, language = {en} } @phdthesis{Flock2021, author = {Flock, Marco}, title = {Velocity Map Imaging-Untersuchung nichtstrahlender Prozesse in polyzyklischen Aromaten und deren van-der-Waals-Clustern}, doi = {10.25972/OPUS-24078}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-240786}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2021}, abstract = {Das erste Ziel der vorliegenden Dissertation bestand darin, ein bereits bestehendes TOF-MS-Setup dahingehend zu erweitern, um damit Velocity Map Imaging-Experimente durchf{\"u}hren zu k{\"o}nnen. Dies erforderte zun{\"a}chst die Konzipierung und Programmierung einiger f{\"u}r die Datenaufnahme, -verarbeitung und -analyse ben{\"o}tigter LabView-Anwendungen. Anschließend konnten erste Kalibrierexperimente an Methyliodid, in denen wichtige experimentelle Parameter identifiziert und optimiert wurden, durchgef{\"u}hrt werden. Außerdem gelang es dadurch, die Messgenauigkeit des Setups auf 0.7 \% und dessen Aufl{\"o}sungsverm{\"o}gen auf 4.4 \% zu bestimmen, was im Bereich f{\"u}r VMI-Apparaturen typischer Werte liegt. Zur weiteren {\"U}berpr{\"u}fung der Funktionst{\"u}chtigkeit des Setups wurde in ersten zeitaufgel{\"o}sten Experimenten im Folgenden die Desaktivierung des S1-Zustands von Pyridin untersucht. Neben der Reproduktion einiger bereits literaturbekannter Resultate konnten dabei zus{\"a}tzlich die im Multiphotonen-Ionisationsschritt populierten Rydberg-Zust{\"a}nde identifiziert werden. Anschließend wurde mit Experimenten an bisher weniger gut untersuchten organischen Aromaten und Heteroaromaten fortgefahren. Das Ziel dieser Studien lag in der Aufkl{\"a}rung der photoinduzierten Dynamiken der Verbindungen, wobei das zur Verf{\"u}gung stehende ps-Lasersystem die M{\"o}glichkeit bot, die Desaktivierung elektronisch angeregter Zust{\"a}nde gezielt in Abh{\"a}ngigkeit von deren Schwingungsenergie zu untersuchen. Der darin bestehende Vorteil zeigte sich vor allem in Studien an Tolan und Phenanthridin, deren erste angeregte, optisch aktive Zust{\"a}nde am Origin Lebensdauern im ns-Bereich aufweisen, die sich mit zunehmender vibronischer Anregung jedoch auf bis zu 10 ps verringern. Als Grund daf{\"u}r konnten nichtstrahlende Desaktivierungsprozesse, f{\"u}r deren Eintreten eine energetische Barriere {\"u}berwunden werden muss, identifiziert werden. W{\"a}hrend in Tolan nach Photoanregung ein {\"U}bergang in einen (πσ∗)-Zustand, der zur Ausbildung einer trans-bent-Struktur f{\"u}hrt, erfolgt, ist im Falle von Phenanthridin vermutlich ein El-Sayed-erlaubter ISC-{\"U}bergang in einen 3(nπ∗)-Zustand f{\"u}r die drastische Verk{\"u}rzung der S1-Lebensdauer verantwortlich. Ein solcher konnte weder im zu Phenanthridin isomerischen Benzo[h]quinolin, noch in dessen PAH-Muttermolek{\"u}l Phenanthren beobachtet werden, was auf die h{\"o}here energetische Lage bzw. die Abwesenheit des mittels ISC populierten 3(nπ∗)-Zustands in diesen Molek{\"u}len zur{\"u}ckgef{\"u}hrt werden kann. In weiteren im Rahmen der vorliegenden Arbeit durchgef{\"u}hrten Experimente wurden zudem die aromatischen Molek{\"u}le Acenaphthylen und 4-(Dimethylamino)benzethin (DMABE) untersucht. Zeitaufgel{\"o}ste Studien zeigten dabei, dass die Desaktivierung der S2-Zust{\"a}nde beider Molek{\"u}le auf der sub-ps-Zeitskala stattfindet und mit dem vorhandenen Lasersystem daher nicht aufgel{\"o}st werden kann. In Acenaphthylen erfolgt die S2-Relaxation gr{\"o}ßtenteils {\"u}ber einen sequentiellen IC-Mechanismus, innerhalb dem der S1-Zustand des Molek{\"u}ls intermedi{\"a}r besetzt wird. Dessen Lebensdauer konnte am Origin auf 380 ps bestimmt werden, f{\"a}llt mit steigender Schwingungsanregung jedoch auf bis zu 55 ps ab. F{\"u}r die Desaktivierung des S2-Zustands von DMABE konnte hingegen ein paralleles Relaxationsmodell, in dem neben dem S1-Zustand ein weiterer elektronisch angeregter Zustand populiert wird, nachgewiesen werden. Bei diesem k{\"o}nnte es sich m{\"o}glicherweise um einen (πσ∗)-Zustand, dessen Besetzung die Ausbildung einer trans-bent-Geometrie innerhalb der Acetylen-Einheit des Molek{\"u}ls zur Folge hat, handeln. Einen weiteren großen Teil der vorliegenden Dissertation nahmen Experimente an van-der-Waals-gebundenen Clustersystemen ein. Im Fokus der Studien standen dabei Molek{\"u}le mit ausgedehnten aromatischen π-Systemen, da solche eine hohe Relevanz f{\"u}r verschiedene materialwissenschaftliche Forschungsgebiete besitzen. Ein Beispiel hierf{\"u}r ist Tetracen, welches als Modellsystem f{\"u}r die Untersuchung von Singlet Fission-Prozessen angesehen wird. In Kombination mit nichtadiabatischen Surface-Hopping-Simulationen zeigten Experimente an Tetracen-Dimeren, dass nach deren S2-Anregung zun{\"a}chst ein schneller S1←S2-{\"U}bergang (τ < 1 ps), gefolgt von der Ausbildung einer Excimerstruktur, stattfindet. Letztere erfolgt mit einer Zeitkonstante von 62 ps und f{\"u}hrt zu einem Anstieg des transienten Ionensignals, wohingegen die Desaktivierung des Excimer-Zustands von einem abklingenden Signalbeitrag mit τ = 123 ps repr{\"a}sentiert wird. Wenngleich {\"u}ber die weitere Relaxation der Excimerspezies zum gegenw{\"a}rtigen Zeitpunkt keine Aussage getroffen werden kann, besteht damit die M{\"o}glichkeit, dass Excimer-Zust{\"a}nde als Zwischenstufe im SF-Mechanismus isolierter Tetracen-Dimere auftreten. In zeitaufgel{\"o}sten Experimenten an Phenanthren-Dimeren konnte ebenfalls ein Anstieg des transienten Signals mit einer vergleichbaren Zeitkonstante von τ = 86 ps, der jedoch auf einem konstanten Signaloffset endet, gefunden werden. Dies deutet darauf hin, dass auch Phenanthren-Dimere in der Lage sind, Excimerstrukturen, die im Gegensatz zu denen des Tetracens jedoch deutlich langlebiger sind, auszubilden. Studien an den Dimerspezies der Azaphenanthrene Benzo[h]quinolin und Phenanthridin offenbarten hingegen etwas schnellere Relaxationen mit Zeitkonstanten von 15 bzw. 40 ps. Zudem zeigten beide Spezies eine stark ausgepr{\"a}gte Fragmentation, sodass f{\"u}r deren Untersuchung auf die VMI-Detektionsmethode zur{\"u}ckgegriffen werden musste. Dadurch wurde deutlich, dass sich Photoionen-Imaging-Experimente hervorragend f{\"u}r Studien an schwach gebundenen Clustersystemen eignen, da diese die Separation verschiedener Signalbeitr{\"a}ge innerhalb eines betrachteten Massenkanals erm{\"o}glichen.}, subject = {Strahlungslose Desaktivierung}, language = {de} } @phdthesis{Becker2015, author = {Becker, Johannes}, title = {Development and implementation of new simulation possibilities in the CAST program package}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-132032}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2015}, abstract = {The aim of the present work is the development and implementation of new simulation possibilities for the CAST program package. Development included, among other things, the partial parallelization of the already existing force fields, extension of the treatment of electrostatic interactions and implementation of molecular dynamics and free energy algorithms. The most time consuming part of force field calculations is the evaluation of the nonbonded interactions. The calculation of these interactions has been parallelized and it could be shown to yield a significant speed up for multi-core calculations compared to the serial execution on only one CPU. For both, simple energy/gradient as well as molecular dynamics simulations the computational time could be significantly reduced. To further increase the performance of calculations employing a cutoff radius, a linkedcell algorithm was implemented which is able to build up the non-bonded interaction list up to 7 times faster than the original algorithm. To provide access to dynamic properties based on the natural time evolution of a system, a molecular dynamics code has been implemented. The MD implementation features two integration schemes for the equations of motion which are able to generate stable trajectories. The basic MD algorithm as described in Section 1.2 leads to the sampling in the microcanonical (NVE) ensemble. The practical use of NVE simulations is limited though because it does not correspond to any experimentally realistic situation. More realistic simulation conditions are found in the isothermal (NVT) and isothermalisobaric (NPT) ensembles. To generate those ensembles, temperature and pressure control has been implemented. The temperature can be controlled in two ways: by direct velocity scaling and by a Nose-Hoover thermostat which produces a real canonical ensemble. The pressure coupling is realized by implementation of a Berendsen barostat. The pressure coupling can be used for isotropic or anisotropic box dimensions with the restriction that the angles of the box need to be 90� . A crucial simulation parameter in MD simulations is the length of the timestep. The timestep is usually in the rang of 1fs. Increasing the timestep beyond 1fs can lead to unstable trajectories since the fastest motion in the system, usually the H-X stretch vibration can not be sampled anymore. A way to allow for bigger timesteps is the use of a constraint algorithm which constrains the H-X bonds to the equilibrium distance. For this the RATTLE algorithm has been implemented in the CAST program. The velocity Verlet algorithm in combination with the RATTLE algorithm has been shown to yield stable trajectories for an arbitrary length of simulation time. In a first application the MD implementation is used in conjunction with the MOPAC interface for the investigation of PBI sidechains and their rigidity. The theoretical investigations show a nice agreement with experimentally obtained results. Based on the MD techniques two algorithms for the determination of free energy differences have been implemented. The umbrella sampling algorithm can be used to determine the free energy change along a reaction coordinate based on distances or dihedral angles. The implementation was tested on the stretching of a deca-L-alanine and the rotation barrier of butane in vacuum. The results are in nearly perfect agreement with literature values. For the FEP implementation calculations were performed for a zero-sum transformation of ethane in explicit solvent, the charging of a sodium ion in explicit solvent and the transformations of a tripeptide in explicit solvent. All results are in agreement with benchmark calculations of the NAMD program as well as literature values. The FEP formalism was then applied to determine the relative binding free energies between two inhibitors in an inhibitor-protein complex. Next to force fields, ab-initio methods can be used for simulations and global optimizations. Since the performance of such methods is usually significantly poorer than force field applications, the use for global optimizations is limited. Nevertheless significant progress has been made by porting these codes to GPUs. In order to make use of these developments a MPI interface has been implemented into CAST for communication with the DFT code TeraChem. The CAST/TeraChem combination has been tested on the \$H_2 O_{10}\$ cluster as well as the polypeptide met-Enkephalin. The pure ab-initio calculations showed a superior behavior compared to the standard procedure where the force field results are usually refined using quantum chemical methods.}, subject = {Molekulardynamik}, language = {en} } @article{OjhaForsterKumaretal.2013, author = {Ojha, Animesh K. and Forster, Stefan and Kumar, Sumeet and Vats, Siddharth and Negi, Sangeeta and Fischer, Ingo}, title = {Synthesis of well-dispersed silver nanorods of different aspect ratios and their antimicrobial properties against gram positive and negative bacterial strains}, series = {Journal of Nanobiotechnology}, volume = {11}, journal = {Journal of Nanobiotechnology}, number = {42}, doi = {10.1186/1477-3155-11-42}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-132222}, year = {2013}, abstract = {In the present contribution, we describe the synthesis of highly dispersed silver nanorods (NRs) of different aspect ratios using a chemical route. The shape and size of the synthesized NRs were characterized by Transmission Electron Microscopy (TEM) and UV-visible spectroscopy. Longitudinal and transverse absorptions bands confirm the rod type structure. The experimentally recorded UV-visible spectra of NRs solutions were fitted by using an expression of the extinction coefficient for rod like nano structures under the dipole approximation. Simulated and experimentally observed UV-visible spectra were compared to determine the aspect ratios (R) of NRs. The average values of R for NR1, NR2 and NR3 solutions are estimated to be 3.0 ± 0.1, 1.8 ± 0.1 and 1.2 ± 0.1, respectively. These values are in good agreement with those obtained by TEM micrographs. The silver NRs of known aspect ratios are used to study antimicrobial activities against B. subtilis (gram positive) and E. coli (gram negative) microbes. We observed that the NRs of intermediate aspect ratio (R = 1.8) have greater antimicrobial effect against both, B. subtilis (gram positive) and E. coli (gram negative). The NRs of aspect ratio, R = 3.0 has better antimicrobial activities against gram positive than on the gram negative.}, language = {en} } @phdthesis{Lang2015, author = {Lang, Melanie}, title = {Valence Shell Photoionization of Soot Precursors with Synchrotron Radiation}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-117038}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2015}, abstract = {A series of combustion relevant species like radicals, carbenes and polycyclic aromatic hydrocarbons were characterized in the gas phase by vacuum UV synchrotron radiation and their ionization energies (IE) and further spectroscopic details of the respective cations were retrieved from threshold photoelectron spectra. The reactive intermediates were generated by flash vacuum pyrolysis from stable precursor molecules. Furthermore three polycyclic aromatic hydrocarbons were investigated by threshold photoelectron spectroscopy, too. The experiment was performed at the VUV beamline of the Swiss Light Source in Villigen/Switzerland and the iPEPICO (imaging photoelectron photoion coincidence) setup was applied to correlate ions and electrons from the same ionization event. From the threshold photoelectron spectra and from quantum chemical computations the vibrational structure of the molecule cations and the geometry changes upon ionization were assigned. The ionization energies of the two C4H5 isomers 2-butyn-1-yl and 1-butyn-3-yl were assigned to 7.94±0.02 eV and 7.97±0.02 eV, respectively. The isomerization between the two isomers was computed to have a barrier of 2.20 eV, so a rearrangement between the two radicals cannot be excluded. From the threshold photoelectron spectra of the two constitutional C4H7 isomers 1-methylallyl and 2-methylallyl the ionization energies were assigned to 7.48±0.02 eV and to 7.59±0.02 eV for 1-E-methylallyl and 1-Z-methylallyl, as well as to 7.88±0.01 eV for 2-methylallyl. The two radicals 9-fluorenyl, C13H9, and benzhydryl, C13H11, were observed to ionize at 7.01±0.02 eV and 6.7 eV. The threshold photoelectron spectrum of benzhydryl also incorporated the signal of the diphenylmethyl carbene, C13H10, which has an IE at 6.8 eV. In addition, the head-to-head dimers of 9-fluorenyl and benzhydryl were observed as products in the pyrolysis. C26H18 has an IE at 7.69±0.04 eV and C26H22 has an IE at 8.13±0.04 eV. The three polycyclic aromatic hydrocarbon DHP (C14H16) 1-PEN (C18H22) and THCT (C22H16) were investigated in an effusive beam. The ionization energies were determined to IE(DHP)= 7.38±0.02 eV, IE(1-PEN)=7.58±0.05 eV and IE(THCT)=6.40±0.02 eV. Furthermore the thermal decomposition and the dissociative photoionization of diazomeldrum's acid was investigated. The pyrolysis products yielded beside several other products the two not yet (by photoelectron spectroscopy) characterized molecules E-formylketene, C3O2H2 and 2-diazoethenone, N2C2O. The dissociative photoionization showed the Wolff rearrangement to occur at higher internal energies.}, subject = {Ultraviolett-Photoelektronenspektroskopie}, language = {en} } @phdthesis{Stehr2015, author = {Stehr, Vera}, title = {Prediction of charge and energy transport in organic crystals with quantum chemical protocols employing the hopping model}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-114940}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2015}, abstract = {As organic semiconductors gain more importance for application, research into their properties has become necessary. This work investigated the exciton and charge transport properties of organic semiconducting crystals. Based on a hopping approach, protocols have been developed for the calculation of Charge mobilities and singlet exciton diffusion coefficients. The protocols do not require any input from experimental data except for the x-ray crystal structure, since all needed quantities can be taken from high-level quantum chemical calculations. Hence, they allow to predict the transport properties of yet unknown compounds for given packings, which is important for a rational design of new materials. Different thermally activated hopping models based on time-dependent perturbation theory were studied for the charge and exciton transport; i. e. the spectral overlap approach, the Marcus theory, and the Levich-Jortner theory. Their derivations were presented coherently in order to emphasize the different levels of approximations and their respective prerequisites. A short reference was made to the empirical Miller-Abrahams hopping rate. Rate equation approaches to calculate the stationary charge carrier mobilities and exciton diffusion coefficients have been developed, which are based on the master equation. The rate equation approach is faster and more efficient than the frequently used Monte Carlo method and, therefore, provides the possibility to study the anisotropy of the transport parameters and their three-dimensional representation in the crystal. The Marcus theory, originally derived for outer sphere electron transfer in solvents, had already been well established for charge transport in organic solids. It was shown that this theory fits even better for excitons than for charges compared with the experiment. The Levich-Jortner theory strongly overestimates the charge carrier mobilities and the results deviate even stronger from the experiment than those obtained with the Marcus theory. The latter contains larger approximations by treating all vibrational modes classically. The spectral overlap approach in combination with the developed rate equations leads to even quantitatively very good results for exciton diffusion lengths compared to experiment. This approach and the appendant rate equations have also been adapted to charge transport. The Einstein relation, which relates the diffusion coefficient with the mobility, is important for the rate equations, which have been developed here for transport in organic crystals. It has been argued that this relation does not hold in disordered organic materials. This was analyzed within the Framework of the Gaussian disorder model and the Miller-Abrahams hopping rate.}, subject = {Exziton}, language = {en} } @phdthesis{Brunecker2015, author = {Brunecker, Frank}, title = {Kohlenstoffnanorohr-Komplexe - Adsorption und Desorption von (Bio-)Polymeren}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-113485}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2015}, abstract = {Zur Charakterisierung der Wechselwirkungen zwischen organischen Dispergiermitteln und nanoskaligen Oberfl{\"a}chen stellen Komplexe aus Kohlenstoffnanor{\"o}hren und (Bio-)Polymeren aufgrund der großen Oberfl{\"a}che der Nanor{\"o}hren und der kommerziellen Verf{\"u}gbarkeit fluoreszenzmarkierter DNA-Oligomere unterschiedlicher L{\"a}nge sowie intrinsisch fluoreszierender Polymere ein vielversprechendes Modellsystem dar. Im Rahmen der vorliegenden Dissertation wurden verschiedene Methoden evaluiert, um die Stabilit{\"a}t derartiger Komplexe zu untersuchen und dadurch R{\"u}ckschl{\"u}sse auf das Adsorptionsverhalten der (Bio-)Polymere zu ziehen. Dabei konnte gezeigt werden, dass das publizierte helikale Adsorptionsmodell der DNA auf Kohlenstoffnanor{\"o}hren die Resultate der durchgef{\"u}hrten Experimente nur unzureichend beschreiben kann und stattdessen andere Adsorptionskonformationen in Erw{\"a}gung gezogen werden m{\"u}ssen.}, subject = {Kohlenstoff-Nanor{\"o}hre}, language = {de} } @phdthesis{Herterich2014, author = {Herterich, J{\"o}rg}, title = {Pikosekunden-zeitaufgel{\"o}ste Photoionisation: 2-Methylallyl-Radikal und Pyracen}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-105829}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2014}, abstract = {Die vorliegende Dissertation untersucht f{\"u}nf unterschiedliche Molek{\"u}le hinsichtlich ihrer Geometrien im Grund- und angeregten Zustand sowie deren Dynamik nach elektronischer Anregung. Der Fokus liegt dabei unter anderem auf Pi-konjugierten Systemen, die {\"u}ber eine zus{\"a}tzliche aliphatische Einheit verbr{\"u}ckt (Paracyclophan- Derivate) oder erweitert (Pyracen) sind. Die Paracyclophan-Derivate sind ein ideales Modellsystem um Einsicht in Pi-Pi-Wechselwirkungen zu erlangen. Ein weiterer Schwerpunkt dieser Arbeit beschreibt die Dynamik des resonanzstabilisierten 2-Methylallyl-Radikals. Die Forschung an solchen kleinen Kohlenwasserstoff-Radikalen ist wichtig, da auf deren Grundlage Modelle entwickelt werden k{\"o}nnen, die zum Beispiel helfen, den Verbrennungsprozess aufzukl{\"a}ren. Aufgrund ihrer Instabilit{\"a}t sind solche kleinen Kohlenwasserstoff-Radikale nicht einfach zu handhaben und das spektroskopische Vermessen stellt immer eine Herausforderung dar.}, subject = {Photoionisation}, language = {de} }