Refine
Has Fulltext
- yes (223)
Is part of the Bibliography
- yes (223)
Year of publication
Document Type
- Doctoral Thesis (137)
- Journal article (67)
- Preprint (19)
Keywords
- Spektroskopie (18)
- Exziton (16)
- Ultrakurzzeitspektroskopie (13)
- Theoretische Chemie (12)
- Femtosekundenspektroskopie (11)
- Kohlenstoff-Nanoröhre (11)
- Raman-Spektroskopie (10)
- Angeregter Zustand (9)
- Molekulardynamik (8)
- Photodissoziation (8)
- Quantendynamik (8)
- Quantenmechanik (8)
- boron (8)
- Einwandige Kohlenstoff-Nanoröhre (7)
- Photoionisation (7)
- Quantenchemie (7)
- REMPI (7)
- quantum dynamics (7)
- Computational Chemistry (6)
- Fotoionisation (6)
- Molekularbewegung (6)
- Optische Spektroskopie (6)
- Photoelektronenspektroskopie (6)
- Synchrotronstrahlung (6)
- Ultrafast spectroscopy (6)
- femtosecond spectroscopy (6)
- radicals (6)
- time-resolved spectroscopy (6)
- Coherent Multidimensional Spectroscopy (5)
- Dichtefunktionalformalismus (5)
- Oberflächenverstärkter Raman-Effekt (5)
- Pump-Probe-Technik (5)
- QM/MM (5)
- SERS (5)
- exciton (5)
- photoelectron spectroscopy (5)
- synchrotron radiation (5)
- Biradikal (4)
- DFT (4)
- Dotierung (4)
- Ladungstransfer (4)
- Laserspektroskopie (4)
- Photolumineszenz (4)
- Photolumineszenzspektroskopie (4)
- Physikalische Chemie (4)
- Radikal <Chemie> (4)
- Theoretical Chemistry (4)
- Velocity-Map-Imaging (4)
- Wellenpaket (4)
- Zeitaufgelöste Spektroskopie (4)
- chemistry (4)
- density functional calculations (4)
- gas phase (4)
- photodissociation (4)
- reactive intermediates (4)
- spectroscopy (4)
- transient absorption (4)
- Absorptionsspektroskopie (3)
- Aggregat <Chemie> (3)
- Bor (3)
- Chemie (3)
- Computational chemistry (3)
- Enzym (3)
- Enzyminhibitor (3)
- Fluoreszenzspektroskopie (3)
- Fotochemie (3)
- Fourier-Spektroskopie (3)
- Freie-Elektronen-Laser (3)
- Infrarot (3)
- Infrarotspektroskopie (3)
- Inhibitor (3)
- Kurzzeitphysik (3)
- Laserstrahlung (3)
- NIR-Spektroskopie (3)
- Nahfeldoptik (3)
- Nanopartikel (3)
- Nichtadiabatischer Prozess (3)
- Nichtlineare Spektroskopie (3)
- Oberflächenplasmonresonanz (3)
- Photochemie (3)
- Polycyclische Aromaten (3)
- Pyrolyse (3)
- Quantum dynamics (3)
- Raman (3)
- Raman Spektroskopie (3)
- Raman spectroscopy (3)
- Resonanz-Raman-Effekt (3)
- Schwingungsspektroskopie (3)
- Surface plasmons (3)
- carbenes (3)
- excited states (3)
- exciton dynamics (3)
- infrared spectroscopy (3)
- organische Halbleiter (3)
- photoionization (3)
- pyrolysis (3)
- reaktive Intermediate (3)
- theoretical chemistry (3)
- time-resolved photoelectron spectroscopy (3)
- 2Dimensionale Spektroskopie (2)
- Ab-initio-Rechnung (2)
- Abstimmbarer Laser (2)
- Adsorption (2)
- Atomic and molecular interactions with photons (2)
- Benchmark (2)
- Berechnung (2)
- Biokompatibilität (2)
- CAAC (2)
- CARS-Spektroskopie (2)
- Chiralität <Chemie> (2)
- Computerphysik (2)
- Conical Intersections (2)
- Cysteinproteasen (2)
- DFT calculations (2)
- Dispergierung (2)
- Dynamik (2)
- EEA (2)
- Electronic spectroscopy (2)
- Elektronische Spektroskopie (2)
- Energietransfer (2)
- Entropie (2)
- Exciton (2)
- Exziton-Exziton-Annihilierung (2)
- Femtochemie (2)
- Femtosekunden (2)
- Fluorescence (2)
- Fluoreszenz (2)
- Fluoreszenzmikroskopie (2)
- Fotophysik (2)
- Gasphase (2)
- Globale Optimierung (2)
- IR spectroscopy (2)
- Infrared and Raman spectroscopy (2)
- Infrarot- und Raman-Spektroskopie (2)
- Infrarot-Spektroskopie (2)
- Interference microscopy (2)
- Kohlenstoffnanoröhre (2)
- Kohärente 2D Spektroskopie (2)
- Kohärente Multidimensionale Spektroskopie (2)
- Kohärente Optik (2)
- Konfokale Mikroskopie (2)
- Laser Pulse Shaping (2)
- Laserchemie (2)
- Laserimpulsformung (2)
- Massenspektrometrie (2)
- Mechanismus (2)
- Metadynamics (2)
- Mikro-Raman-Spektroskopie (2)
- Molecular dynamics (2)
- Molekularstrahl (2)
- Molekülstruktur (2)
- Nonadiabatic quantum dynamics (2)
- Oberfläche (2)
- Optical spectroscopy (2)
- Paracyclophane (2)
- Pericyclische Reaktion (2)
- Photochemistry (2)
- Polarisationspulsformung (2)
- Polychromophores System (2)
- Polycyclic Aromatic Hydrocarbons (2)
- Quantenkontrolle (2)
- Quantum Chemistry (2)
- Reaction kinetics and dynamics (2)
- Reaktionsmechanismus (2)
- Resonanz-Raman (2)
- Scanning microscopy (2)
- Spectroscopy (2)
- Spektroelektrochemie (2)
- Strukturaufklärung (2)
- Störungstheorie (2)
- TEM (2)
- Transiente Absorption (2)
- Transiente Absorptionsspektroskopie (2)
- Ultrakurzer Lichtimpuls (2)
- Ultraschnelle Photochemie (2)
- Ultraviolett-Photoelektronenspektroskopie (2)
- Vierwellenmischung (2)
- Zeitauflösung (2)
- Zwei-Sechs-Halbleiter (2)
- ab initio calculations (2)
- absorption spectra (2)
- antimicrobial activities (2)
- benzyl radical (2)
- biradicals (2)
- carbene ligands (2)
- catalysis (2)
- computational chemistry (2)
- covalent inhibitors (2)
- diborane (2)
- diborenes (2)
- diradicals (2)
- exciton-exciton (2)
- femtochemistry (2)
- fluorescence (2)
- free electron laser (2)
- heterocycles (2)
- infrared (2)
- inorganic chemistry (2)
- laser (2)
- mechanism (2)
- microscopy (2)
- molecular dynamics (2)
- molecular switch (2)
- nano rods (2)
- nanostructures (2)
- nonadiabatic dynamics (2)
- optical spectroscopy (2)
- organic semiconductors (2)
- photoionisation (2)
- photolysis (2)
- prodrug (2)
- protease (2)
- pulse shaping (2)
- pyrene dimer (2)
- quantum chemistry (2)
- resonance Raman (2)
- rhodesain (2)
- self-assembly (2)
- silver (2)
- ultrafast photochemistry (2)
- zeitaufgelöste Spektroskopie (2)
- Übergangsmetallkomplexe (2)
- (6,5) carbon nanotubes (1)
- (6,5)-Kohlenstoffnanoröhre (1)
- (6,5)-Kohlenstoffnanoröhren (1)
- (6,5)-SWNT (1)
- (6,5)-Spektroskopie (1)
- 1,4-naphthoquinone (1)
- 2-Methylallyl (1)
- 2-methylallyl (1)
- Accumulative Femtosecond Spectroscopy (1)
- Aerosol (1)
- African sleeping sickness (1)
- Aggregation (1)
- Airborne particles (1)
- Allyl (1)
- Allylradikal (1)
- Anisotropie (1)
- Anrege-Abfrage-Spektroskopie (1)
- Anthracen (1)
- Aqueous Solution Photochemistry (1)
- Arzneimittel (1)
- Astrochemie (1)
- Aufladung (1)
- Auge (1)
- Auger-Spektroskopie (1)
- Autodetachment (1)
- BZ reaction (1)
- BZ-Reaktion (1)
- Barbituric Acid Merocyanines (1)
- Basin-Hopping (1)
- Belousov-Zabotinskij-Reaktion (1)
- Benzylradikal (1)
- Beschallung (1)
- Bimolekulare Reaktion (1)
- Bio Nano Technology (1)
- Bio-Nano-Technologie (1)
- Biologisches Material (1)
- Biomolekül (1)
- Biradical (1)
- Biradicals (1)
- Biradikale (1)
- Blutkontakt (1)
- Blutzucker (1)
- Bor-Carbonylkomplexe (1)
- Born-Oppenheimer-Näherung (1)
- Borole (1)
- CARS (1)
- CC2 (1)
- CCD (1)
- CCD, charge-coupled device (1)
- CD-Spektroskopie (1)
- CVD Synthese (1)
- Caging (1)
- Carbene (1)
- Carbon Nanotube (1)
- Carbonyl- (1)
- Carrier envelope phase effects (1)
- Charge carrier characterization (1)
- Chemical Dynamics (1)
- Chemical Structure (1)
- Chemische Analyse (1)
- Chemische Bindung (1)
- Chemisorption (1)
- Circular dichroism spectroscopy (1)
- Clusteranalyse (1)
- Coherent 2D Spectroscopy (1)
- Coherent 2D spectroscopy (1)
- Coherent Two-dimensional Nanoscopy (1)
- Coherent control (1)
- Coherent two-dimensional Spectroscopy (1)
- Colloid Chemistry (1)
- Combustion (1)
- Computational Investigation (1)
- Computational physics (1)
- Computerchemie (1)
- Conical Intersection (1)
- Coronaviren (1)
- Coupled Cluster (1)
- Coupled Electron-Nuclear Dynamics (1)
- Cyclophane (1)
- DFT and ab-initio calculations (1)
- DFT- und ab-initio-Rechnungen (1)
- DFT-Berechnungen (1)
- DFT-Rechnungen (1)
- DNA (1)
- DNA-SWNT hybrids (1)
- DNA-SWNT-Konjugate (1)
- DNS (1)
- Decarbonylierung (1)
- Desorption (1)
- Diboran (1)
- Diborylalkene (1)
- Dichtefunktionalrechnungen (1)
- Dichtefunktionsformalismus (1)
- Dichtegradientenultrazentrifugation (1)
- Dielektrizitätszahl (1)
- Differential Shannon Entropy (1)
- Diffusion (1)
- Dimension 2 (1)
- Dimermethode (1)
- Dissipatives System (1)
- Dissoziative Photoionisation (1)
- Doppelquantenkohärenz (1)
- Doppelresonanz (1)
- Doppler-Verbreiterung (1)
- Dünne Schicht (1)
- EDA-NOCV (1)
- EGA-FTIR (1)
- Effekte der absoluten Phase (1)
- Einzelmolekülmikroskopie (1)
- Einzelmolekülspektroskopie (1)
- Einzelstrang-DNA (1)
- Eisen (1)
- Electrodynamic trap (1)
- Electron Flux (1)
- Elektrochemie (1)
- Elektrodynamische Falle (1)
- Elektrolyse (1)
- Elektronen-Kernbewegung (1)
- Elektronendichte (1)
- Elektronenlokalisierung (1)
- Elektronenspektroskopie (1)
- Elektronenstrahlmikrosonde (1)
- Elektronentransferdynamik (1)
- Elektronische Anregung (1)
- Energiehyperfläche (1)
- Energielandschaft (1)
- Entladung (1)
- Enzymkatalyse (1)
- Erregbarkeit (1)
- Ethyl (1)
- Ethylen- (1)
- Ethylradikal (1)
- Evaporation-Induced Self-Assembly (1)
- Excited state dynamics (1)
- Excited states (1)
- Excited-State Dynamics of Organic Intermediates (1)
- Exciton dynamics (1)
- Exciton localization dynamics (1)
- Excitons (1)
- Exciton–exciton annihilation (1)
- Exziton-Exziton-Anihillierung (1)
- Exzitonen (1)
- Exzitonendynamik (1)
- Exzitonengröße (1)
- Exzitonentransport (1)
- FL spectroscopy (1)
- FT-Raman (1)
- FT-Raman spectroscopy (1)
- FT-Raman-Spektroskopie (1)
- Falle (1)
- Fasersonde (1)
- Fel (1)
- Femto-chemistry (1)
- Femtochemistry (1)
- Femtosecond (1)
- Femtosecond Mid-Infrared Study (1)
- Femtosecond Pulse Shaping (1)
- Femtosecond Spectroscopy (1)
- Femtosekunden Pulsformung (1)
- Femtosekunden Spektroskopie (1)
- Femtosekunden zeitaufgelöste Spektroskopie (1)
- Femtosekunden-Spektroskopie (1)
- Femtosekundenbereich (1)
- Femtosekundenlaser (1)
- Festkörperstrukturen (1)
- Flugzeitmassenspektrometrie (1)
- Fluoreszenzverstärkung (1)
- Fluorochinolon (1)
- Flussdichte (1)
- Force Field (1)
- Fotolyse (1)
- Four-Wave Mixing (1)
- Fourier-transform spectral interferometry (1)
- Free Electron Laser (1)
- Free Energy Perturbation (1987 : Princeton, NJ) (1)
- Freie Enthalpie (1)
- Frequenzumsetzung (1)
- Frequenzumwandlung (1)
- Fulminsäure (1)
- Funktionalisierung (1)
- Funktionalisierung <Chemie> (1)
- Förster coupling (1)
- Förster-Kopplung (1)
- G protein-coupled receptor (1)
- G-Protein-gekoppelter Rezeptor (1)
- Gas-Phase (1)
- Gelfilm (1)
- Geometric Phase (1)
- Gibbs Energy (1)
- Grundzustand (1)
- Halbleiter (1)
- Halogene (1)
- Hartree-Fock-Methode (1)
- HeLa-Zelle (1)
- Heparin (1)
- Heterocyclen (1)
- High-excited electronic states (1)
- Higher-order Transient Absorption Spectroscopy (1)
- Hochangeregte elektronische Zustände (1)
- Hohe Harmonische (1)
- Host-Guest Interaction (1)
- Hydrocarbon radicals (1)
- Hydrocarbons (1)
- Hydrogel (1)
- Hydrogen (1)
- ICD (1)
- II-VI-Halbleiter-Nanopartikel (1)
- II-VI-semiconductor nanoparticles (1)
- IR/UV Ion Dip Spectroscopy (1)
- ISRS (1)
- Implantat (1)
- Impulsformung (1)
- Inhibition (1)
- Intermediate (1)
- Intersystem Crossing (1)
- Iod (1)
- Iodine (1)
- Iodmolekül (1)
- Ion-Dip-Spectroscopy (1)
- Ionisationsenergie (1)
- Isomer (1)
- Isonitril- (1)
- Isotopieeffekt (1)
- Jahn–Teller effect (1)
- Kammerwasser (1)
- KasA (1)
- Katalyse (1)
- Ketene (1)
- Kinetics (1)
- Kinetik (1)
- Kohlenwasserstoffen (1)
- Kohärente Anregung (1)
- Kohärente Kontrolle (1)
- Kolloidchemie (1)
- Komplexe (1)
- Konische Durchschneidung (1)
- Konischen-Durschneidung (1)
- Kontrolltheorie (1)
- Konzentrationssprungmethode (1)
- Kooperativität (1)
- Koordinationsverbindungen (1)
- Korrelationsfunktion zweiter Ordnung (1)
- Kosmochemie (1)
- Kraftfeld (1)
- Kraftfeld-Rechnung (1)
- Kupfer- und Eisen-dotierten Glas-Systemen (1)
- Käfig-Rekombination (1)
- LCD Pulse Shaper (1)
- LCD Pulsformer (1)
- Ladungstransport (1)
- Ladungsträger (1)
- Ladungsträger-Charakterisierung (1)
- Ladungsträgererzeugung (1)
- Ladungsträgerlokalisation (1)
- Lanthanidkomplexe (1)
- Laser (1)
- Laser pulse shaping (1)
- Laser-Kontrolle (1)
- Laserinduzierte Fluoreszenz (1)
- Laserpulsformung (1)
- Lebensdauer (1)
- Lebensmittelzusatzstoffe (1)
- Lewis acidity (1)
- Licht-Sammel-Komplex (1)
- Ligand (1)
- Lipide (1)
- Lithium niobate (1)
- Lokalisation (1)
- Low energy electron microscopy LEEM (1)
- Lumineszenz (1)
- Lösungsmitteleffekt (1)
- MIRAS (1)
- MP-Störungstheorie (1)
- Marcus Theory (1)
- Marcus-Theorie (1)
- Mars Meteoriten (1)
- Mars Meteorites (1)
- Mehrphotonen-Spektroskopie (1)
- Mehrphotonenprozess (1)
- Meisenheimer complex (1)
- Merocyanine (1)
- Metadynamik (1)
- Metal clusters (1)
- Methodenentwicklung (1)
- Microcapsules (1)
- Microorganismen (1)
- Mie Theorie (1)
- Mie Theory (1)
- Mikrofluidikchip (1)
- Mikrokapseln (1)
- Mikroorganismus (1)
- Mikroskopie (1)
- Mikrosolvatation (1)
- Mizelle (1)
- Molecular Dynamics (1)
- Molecular Phenomena (1)
- Molecular Simulation (1)
- Molecular Structure (1)
- Molecular mechanics (1)
- Molecular motion (1)
- Molekular Dynamik (1)
- Molekulardesign (1)
- Molekulare Phänomene (1)
- Molekularmechanik (1)
- Molekül (1)
- Moleküldynamik (1)
- Molekülphysik (1)
- Molekülzu (1)
- Molekülzustand (1)
- Monte-Carlo-Simulation (1)
- Mosaikgläser (1)
- Multi-Photonen Prozesse (1)
- Multidimensionale Spektroskopie (1)
- Multikernpartikel (1)
- N ligands (1)
- NEVPT2 (1)
- NEXAFS (1)
- NHC (1)
- NIR (1)
- NIR-spectroscopy (1)
- NMR spectroscopy (1)
- Nahinfrarot (1)
- Nano-Partikel (1)
- Nano-optics (1)
- Nanomaterialien (1)
- Nanomaterials (1)
- Nanooptic (1)
- Nanooptics (1)
- Nanorohr-Polymer-Komplexe (1)
- Nanoröhre (1)
- Nanostruktur (1)
- Nicht-Störungstheoretisch (1)
- Nicht-adiabatische Dynamik (1)
- Nichtinvasive Diagnostik (1)
- Nichtlineare Dynamik (1)
- Nichtlineare Optik (1)
- Nichtlineare Welle (1)
- Nichtlineares Phänomen (1)
- Nichtlinearität (1)
- Nichtstarres Molekül (1)
- Non-adiabatic Dynamics (1)
- Nonadiabatic Dynamics (1)
- Nonadiabatic dynamics (1)
- Nonlinear Dynamics (1)
- Nonlinearity (1)
- Nucleobase Surrogate Incorporation (1)
- Numerische Physik (1)
- Numerische Verfahren (1)
- Oberflächen-verstärkte Raman Streuung (SERS) (1)
- Oberflächenmodifizierung (1)
- Oberflächenplasmon (1)
- Oligonucleotide (1)
- Optical Activity (1)
- Optische Gradientenfalle (1)
- Organischer Halbleiter (1)
- Orientiertes Molekül (1)
- Orientierung (1)
- Oszillator (1)
- Oxygen-Oscillator (1)
- PA-MBO-System (1)
- PAH formation (1)
- PCI (1)
- PDMS-Membranen (1)
- PDMS-membranes (1)
- PES (1)
- PI-System (1)
- PLE spectroscopy (1)
- PLE-Spektroskopie (1)
- Perylenbisimid (1)
- Perylenderivate (1)
- Pflanzen (1)
- Pharmazeutika (1)
- Phase cycling (1)
- Phasenmodulation (1)
- Phosphor (1)
- Phosphoresence (1)
- Photodynamics (1)
- Photoelektron-Photoion-Koinzidenz (1)
- Photoelektronen-Photoionen-Koinzidenz (1)
- Photoelektronen-Spektroskopie (1)
- Photoemission electron microscopy PEEM (1)
- Photoemissionselektronenmikroskopie (1)
- Photofragmentspektroskopie (1)
- Photolysis (1)
- Photonenecho (1)
- Photophysik (1)
- Photorezeptor (1)
- Physical chemistry (1)
- Physik (1)
- Physikalische Theorie (1)
- Physisorption (1)
- Pigmente (1)
- Pigments (1)
- Plasmon propagation (1)
- Plasmonics (1)
- Polarisiertes Licht (1)
- Polyatomare Verbindungen (1)
- Polyfluorene (1)
- Porphyrin (1)
- Porphyrin arrays (1)
- Porphyrine (1)
- Potentialinduzierte Löschung (1)
- Predissociation (1)
- Prolin (1)
- Propargyl (1)
- Propolis (1)
- Protease (1)
- Proteaseinhibitor (1)
- Proteindesign (1)
- Proteine (1)
- Protonentransfer (1)
- Protonierung (1)
- Provitamin A (1)
- Prädissoziation (1)
- Pulse shaping (1)
- Pulsformung (1)
- Pump-CARS (1)
- Pump-Probe Technik (1)
- Pump-Probe-Spektroskopie (1)
- Pump–probe spectroscopy (1)
- Purin (1)
- Pyracen (1)
- Pyrenderivate (1)
- Pyrimidinderivate (1)
- QD's symmetry (1)
- QM (1)
- Quamtum chemistry (1)
- Quantenelektrodynamik (1)
- Quantenmechanisches System (1)
- Quantentheoretische Chemie (1)
- Quantentheorie (1)
- Quantisierung <Physik> (1)
- Quantum Plasmonics (1)
- Quantum-Jump-Ansatz (1)
- Radicals (1)
- Radikal (1)
- Radikale (1)
- Raman Scattering (1)
- Raman Spectroscopy (1)
- Raman microspectroscopy (1)
- Raman-Effekt (1)
- Raman-scattering (1)
- Reaction Mechanism (1)
- Reactive Hydrocarbon Species (1)
- Reaktions-Diffusions-Systeme (1)
- Reaktionskinetik (1)
- Reaktionspfadsuche (1)
- Reaktive Intermediate (1)
- Reaktive Zwischenstufe (1)
- Redoxpotential (1)
- Reduktionen (1)
- Relaxation (1)
- Relaxation Dynamics (1)
- Resonance Raman (1)
- Resonance Raman Effect (1)
- Resonance Stabilized Radicals (1)
- Resonanz-Raman-Spektroskopie (1)
- Rhodium (1)
- Rumpfniveauanregung (1)
- Röntgenabsorptionsfeinstruktur (1)
- Röntgenpulverdiffraktometrie (1)
- SAPT (1)
- SARS (1)
- SF-DFT (1)
- SHB (1)
- STIRAP (1)
- SWNT-Ensemble (1)
- SWNT-ensemble (1)
- Sauerstoff (1)
- Sauerstoff-Oszillatoren (1)
- Schermischen (1)
- Schwebeteilchen (1)
- Sekundärmetabolit (1)
- Sekundärstruktur (1)
- Selbstorganisation (1)
- Self-Trapping (1)
- Shin-Metiu Model (1)
- Shin-Metiu-Modell (1)
- SiC vacancy defects (1)
- SiC-Fehlstellendefekte (1)
- Siliciumcarbid (1)
- Silyl-Komplexen (1)
- Simulation (1)
- Single-molecule microscopy (1)
- Solarzelle (1)
- Sorptionsstudien (1)
- Sparse Sampling (1)
- Spatially resolved 2D spectroscopy (1)
- Spektrale Diffusion (1)
- Spektrale Interferenz (1)
- Sprungmodell (1)
- Squaraine (1)
- Stent (1)
- Stochastische Resonanz (1)
- Stochastischer Prozess (1)
- Strahlungslose Desaktivierung (1)
- Strahlungsloser Übergang (1)
- Struktur-Aktivitäts-Beziehung (1)
- Substrat <Chemie> (1)
- Subwavelength structures (1)
- Surface Enhanced Raman Scattering (1)
- Surface Plasmon (1)
- Surface enhance Raman scattering (SERS) (1)
- Symmetrie der Quantenpunkte (1)
- Synchrotron (1)
- Synchrotron Radiation (1)
- Synthetische Polypeptide (1)
- System-Bad-Ansatz (1)
- T cells (1)
- TD-DFT (1)
- TICT (1)
- TPES (1)
- Tabu-Search (1)
- Tectosilicate (1)
- Temperaturabhängigkeit (1)
- Tensid (1)
- Theoretische Physik (1)
- Thermoanalyse (1)
- Thioaldehyd- (1)
- Time-Resolved Spectroscopy (1)
- Time-resolved photoemission electron microscopy (1)
- Time-resolved spectroscopy (1)
- Titan (1)
- Transient Absorption Spectroscopy (1)
- Transient Grating (1)
- Transient-Absorption Sectroscopy (1)
- Transiente Gitter (1)
- Transiente Spektroskopie (1)
- Truxenon (1)
- Tuberkelbakterium (1)
- Two-color pump-probe spectroscopy (1)
- Two-dimensional Spectroscopy (1)
- Two-dimensional spectroscopy (1)
- UV-Spektroskopie (1)
- UV-VIS-Spektroskopie (1)
- UV-spectroscopy (1)
- UV/Vis spectroscopy (1)
- Ultrafast Spectroscopy (1)
- Ultrafast information processing (1)
- Ultrafast measurements (1)
- Ultrakurzzeit Spektroskopie (1)
- Ultrakurzzeitlaser (1)
- Ultrashort pulse lasers (1)
- Ultraviolettlaser (1)
- Umbrella Sampling (1)
- Umgebungseffekte (1)
- Umgebungseinfluss (1)
- Umlagerungen (1)
- Ungesättigte Verbindungen (1)
- Upconversion (1)
- Vakuum Jet-Flash Pyrolyse (1)
- Valenzgemischte Verbindungen (1)
- Van-der-Waals-Cluster (1)
- Vektor (1)
- Vektorfeldformer (1)
- Vektorfeldkontrolle (1)
- Velocity Map Imaging (1)
- Verbindungen (1)
- Verdunstung (1)
- Verzögerte Fluoreszenz (1)
- Vierwellenmischen (1)
- Vinyliden- (1)
- Wandmalerei (1)
- Wasserstoffatom (1)
- Wasserstoffionenkonzentration (1)
- Wellenpaketdynamik (1)
- Wirkstoff (1)
- Wirkstoffe (1)
- Wirt-Gast-Wechselwirkung (1)
- Wolfram (1)
- X-ray diffractometry (1)
- ZEKE (1)
- Zeitaufgelöste Photolumineszenz (1)
- Zeolites (1)
- Zeolithe (1)
- Zirkulardichroismus Spektroskopie (1)
- Zusatzstoff (1)
- Zwei-Dimensional (1)
- Zweiatomiges Molekül (1)
- Zweidimensionale Spektroskopie (1)
- Zweidimensionale elektronische Spektroskopie (1)
- Zwischenmolekulare Kraft (1)
- acenes (1)
- acid-sensitive (1)
- active agents (1)
- adsorption (1)
- allyl (1)
- amino-acids (1)
- ammonia borane (1)
- amphiphilic systems (1)
- ancient coloured glass (1)
- angeregte Zustände in Aggregaten (1)
- anisotropy (1)
- antiaromaticity (1)
- aqueous humor (1)
- aromaticity (1)
- artificial light harvesting systems (1)
- atomic physics (1)
- basin hopping (1)
- benchmark (1)
- beryllium (1)
- beta substitution (1)
- beta-Carotene (1)
- beta-Carotin (1)
- beta-Substitution (1)
- biocompatibility (1)
- biological photoreceptors (1)
- biologically active molecules (1)
- biologisch aktiven Moleküle (1)
- biologische Photorezeptoren (1)
- bismuth (1)
- blood-contact (1)
- bond Activation (1)
- bond theory (1)
- bonding (1)
- borole (1)
- boron tetraiodide (1)
- bunte Glasperlen (1)
- cameras (1)
- carbohydrates (1)
- carbon monoxide (1)
- carbon nanotube (1)
- carbon nanotubes (1)
- carbon nanotubes and fullerenes (1)
- carbonyl complexes (1)
- catalytic mechanism (1)
- cationic species (1)
- cell differentiation (1)
- charge carrier generation (1)
- charge carrier localization (1)
- charge transfer (1)
- charge-coupled device (1)
- charging (1)
- chemical bonding (1)
- chiral control (1)
- chirale Kontrolle (1)
- cholera (1)
- circularly-polarized light (1)
- cluster analysis (1)
- coherent anti-Stokes Raman scattering (1)
- coherent anti-Stokes Raman scattering (CARS) (1)
- coherent multidimensional spectroscopy (1)
- coherent spectroscopy (1)
- computational physics (1)
- confocal micro-Raman spectroscopy (1)
- conical intersections (1)
- control theory (1)
- coordination compounds (1)
- copper and iron doped glass systems (1)
- core level excitation (1)
- coupled electron-nuclear motion (1)
- coupled nuclear-electron MCTDH (1)
- covalent and non-covalent inhibitors (1)
- covalent functionalization (1)
- covalent reversible inhibition (1)
- cyclophanes (1)
- cystein protease inhibitor QSAR (1)
- cysteine protease (1)
- cytokines (1)
- delayed fluorescence (1)
- density functional theory (1)
- density gradient ultracentrifugation (1)
- dichroism (1)
- dimer method (1)
- discharge (1)
- dissipative Umgebung (1)
- dissipative environments (1)
- dissociative photoionisation (1)
- dissoziative Photoionisation (1)
- doppler broadening (1)
- dye chemistry (1)
- dünner Filme (1)
- electric field distribution (1)
- electrochemistry (1)
- electron density (1)
- electron localization (1)
- electron transfer dynamics (1)
- electronic (1)
- electronic excitation (1)
- electronisch (1)
- electrophilic (het)arene (1)
- electrophilic substitution (1)
- elektrochemische Bandlücke (1)
- elektronisch angeregte Zustände (1)
- energy landscapes (1)
- energy transfer dynamics (1)
- entropy (1)
- environmental effects (1)
- essential oils (1)
- ethyl (1)
- ethylene complexes (1)
- exact conical intersection dynamics (1)
- exact wave function (1)
- exakte Wellenfunktion (1)
- excimer formation (1)
- excitability (1)
- excited state (1)
- excited states in aggregates (1)
- exciton exciton annihilation (1)
- exciton size (1)
- exciton transfer (1)
- exciton transport (1)
- excitons (1)
- eye (1)
- femtosecond (1)
- femtosecond pulse shaping (1)
- femtosecond pump-probe spectroscopy (1)
- femtosecond time-resolved spectroscopy (1)
- fiber probe (1)
- field-induced surface hopping (1)
- fluorescence quantum yield (1)
- fluorescence spectra (1)
- food additives (1)
- four wave mixing spectroscopy (1)
- free jet (1)
- free-base porphyrins (1)
- frequency conversion (1)
- geformte Laserfelder (1)
- gemischtvalente Verbindung (1)
- gemischvalente Verbindungen (1)
- gold nanoparticles (1)
- ground states (1)
- halides (1)
- heparin (1)
- high energy (1)
- high harmonic generation (1)
- high-temperature chemistry (1)
- higher lying electronic states (1)
- homochirality (1)
- hopping model (1)
- hybrid Polymer-Schichten (1)
- hybrid polymer coatings (1)
- hydration dynamics (1)
- hydrocarbon (1)
- hydrogel (1)
- hydrogen bonding (1)
- hydrogen storage (1)
- hydrolysis (1)
- immune evasion (1)
- in vitro study (1)
- information-theoretical (1)
- infrared-spectra (1)
- inhibition (1)
- inhibitor (1)
- innere Umwandlung (1)
- intermediate (1)
- ionization energy (1)
- ionization potential (1)
- isolierte Moleküle (1)
- isonitrile complexes (1)
- katalytischer Mechanismus (1)
- kinetics (1)
- kohärente anti-Stokessche Raman-Spektroskopie (CARS) (1)
- kohärente anti-Stokessche Raman-Streuung (1)
- konfokal Mikro-Raman-Spektroskopie (1)
- konische Durchschneidung (1)
- kovalent-reversible Hemmung (1)
- kovalent-reversible Inhibitoren (1)
- kovalente Funktionalisierung (1)
- kovalente und nicht-kovalente Enzym-Inhibitor-Komplexe (1)
- künstliche Lichtsammelsysteme (1)
- lanthanide complexes (1)
- laser control (1)
- laser spectroscopy (1)
- length scale (1)
- lipids (1)
- luminescence (1)
- main group elements (1)
- manganese (1)
- merocyanine (1)
- metal cluster (1)
- metal-cluster hybrid systems (1)
- metal-metal interactions (1)
- metallfreie Porphyrine (1)
- metallic (1)
- metallisch (1)
- method development (1)
- methyl exchange (1)
- methylbismuth (1)
- micelle (1)
- micro Raman spectroscopy (1)
- microfluidic chip (1)
- microorganisms (1)
- microprobe analysis (1)
- microsolvation (1)
- mixed valence compound (1)
- mixed-valence compound (1)
- modulators (1)
- molecular mechanics (1)
- molecular orbitals (1)
- molecular physics (1)
- molekulare Schalter (1)
- multi-photon processes (1)
- multicore particles (1)
- multicycle CEP control (1)
- multidimensional spectroscopy (1)
- multiphoton spectroscopy (1)
- nano particle (1)
- nano-particle (1)
- nanocavities (1)
- nanophotonics and plasmonics (1)
- nanotube (1)
- nanotube-polymer-complexes (1)
- nanowire formation (1)
- naphthyridine (1)
- natural products (1)
- neue metallorganische Komplexe (1)
- new organometallic complexes (1)
- nicht-adiabatische Effekte (1)
- nicht-invasiv (1)
- nichtadiabatische Kopplung (1)
- nichtlineare Optik (1)
- niederdimensionale Halbleiter (1)
- nitrogen trichloride (1)
- non-invasive (1)
- nonadiabatic Dynamics (1)
- nonadiabatic coupling (1)
- nonadiabatic effects (1)
- noncovalent interactions (1)
- nonlinear optics (1)
- nonlinear spectroscopy (1)
- nonradiative Relaxation (1)
- nucleophilic addition (1)
- nucleophilic aromatic substitution (1)
- open-shell molecules (1)
- optical gradient trap (1)
- optical response (1)
- optics (1)
- organic electronics (1)
- organic interfaces (1)
- organische Grenzflächen (1)
- organometallic chemistry (1)
- oxidation (1)
- oxidative addition (1)
- p-block element (1)
- particles (1)
- peptidomimetic sequence (1)
- pericyclic reaction (1)
- pharmaceuticals (1)
- phosphorus heterocycles (1)
- photoactivation (1)
- photochemical processes (1)
- photochemische Prozesse (1)
- photodynamics (1)
- photoelectron-photoion coincidence (1)
- photoluminescence (1)
- photonic devices (1)
- pi-pi interaction (1)
- pi-pi-Wechselwirkung (1)
- pincer ligand (1)
- plasmon group velocity (1)
- plasmonic waveguides (1)
- platinum (1)
- polarisation pulse shaping (1)
- polarization pulse shaping (1)
- polarized low wavenumber Raman spectroscopy (1)
- polymers (1)
- porphyrin (1)
- potassium reagent (1)
- proline (1)
- propargyl (1)
- propolis (1)
- protease inhibitors (1)
- protein (1)
- protein design (1)
- protein hydration (1)
- proteins (1)
- protonation (1)
- pump-CARS (1)
- pump-probe-spectroscopy (1)
- purine (1)
- pyracene (1)
- pyrimidines (1)
- quantum control (1)
- quantum dots (1)
- quantum mechanics (1)
- quantum optics (1)
- rBAM2-labeled RNA strands (1)
- radical reactions (1)
- reaction mechanisms (1)
- reaction-diffusion-systems (1)
- reactivity and selectivity study (1)
- reductive alkylation (1)
- reduktive Alkylierung (1)
- regulatory T cells (1)
- resonance Raman scattering (1)
- s-block metals (1)
- schwach gekoppelte Regime (1)
- second-order correlation function (1)
- secondary structure (1)
- self-trapping (1)
- semiconductor nanostructures (1)
- simulation (1)
- single particle microscopy (1)
- single-wall carbon nanotube (1)
- small interfering RNAs (1)
- solar cell (1)
- solar fuels (1)
- solid-state sturcture (1)
- solvent effects (1)
- solvent-dependent fluorescence yield (1)
- solvents (1)
- sorption studies (1)
- squaraine polymer (1)
- stent (1)
- stochastic resonance (1)
- stochastische Schrödingergleichung (1)
- strong coupling (1)
- structural biology (1)
- superstructure (1)
- supramolecular folding (1)
- supramolecular materials (1)
- surface (1)
- surface modifications (1)
- synchrotron radiatoren (1)
- synthetic polypeptides (1)
- temperature dependence (1)
- tetracene dimer (1)
- thin film (1)
- threshold photoelectron photoion coincidence (1)
- threshold photoelectron spectroscopy (1)
- time resolved spectroscopy (1)
- time-dependent density functional theory (1)
- time-resolved optical spectroscopy (1)
- time-resolved photoluminescence (1)
- titanium (1)
- total electric field (1)
- toxins (1)
- trans-formanilide (1)
- transient absorption spectroscopy (1)
- transient spectroscopy (1)
- transiente Absorption (1)
- transiente Absorptionsspektroskopie (1)
- transition charge (1)
- transition density (1)
- transition dipole moment (1)
- transition metal complexes (1)
- transition metal dichalcogenide (1)
- trap (1)
- truxenone (1)
- ultrafast measurements (1)
- ultrafast spectroscopy (1)
- ultrashort time (1)
- ultraviolet light (1)
- van der Waals Clustern (1)
- van der Waals clusters (1)
- vector-field control (1)
- vector-field shaper (1)
- verdunstungsinduzierter Selbstanordnung (1)
- verzögerte Fluoreszenz (1)
- vibrational spectroscopy (1)
- vier Wellen Mischen Spektroskopie (1)
- vinylidene complexes (1)
- wallpainting (1)
- warhead (1)
- water migration (1)
- water oxidation (1)
- wave functions (1)
- weak coupling regime (1)
- xylylene (1)
- zeitabhängige Dichtefunktionaltheorie (1)
- Übergangsmetalldichalkogenide (1)
- Übergangszustand (1)
- ätherische Öle (1)
- π-complex (1)
- π-conjugated systems (1)
Institute
- Institut für Physikalische und Theoretische Chemie (223) (remove)
Sonstige beteiligte Institutionen
- Arizona State University, Tempe, Arizona, USA (1)
- Center for Nanosystems Chemistry (CNC), Universität Würzburg (1)
- Center for Nanosystems Chemistry (CNC), Universität Würzburg, Am Hubland, 97074 Würzburg, Germany (1)
- Center of Excellence for Science and Technology - Integration of Mediterranean region (STIM), Faculty of Science, University of Split, Poljička cesta 35, 2100 Split, Croatia (1)
- Charles University, Faculty of Mathematics and Physics, Ke Karlovu 5, 121 16 Prague, Czech Republic (1)
- Departamento de Química, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid, Spain (1)
- Department of Chemistry, Humboldt Universität zu Berlin, Brook-Taylor-Strasse 2, 12489 Berlin, Germany (1)
- Department of Chemistry, Sungkyunkwan University, 440-746 Suwon, Republic of Korea (1)
- Fachbereich Physik, Universität Konstanz, D-78464 Konstanz, Germany (1)
- Fakultät für Physik, Universität Bielefeld (1)
ResearcherID
- B-1911-2015 (1)
- M-1240-2017 (1)
- N-3741-2015 (1)
Im Rahmen dieser Dissertation wurden insgesamt drei verschiedene Fragestellungen an biologisch relevanten Modellsystemen mit Hilfe von diversen linearen und nichtlinearen Raman-spektroskopischen Techniken bearbeitet. Neben der Untersuchung von Wasserstoffbrücken-gebundenen Komplexen und ihrer Dynamik auf der fs-Zeitskala (Kapitel 4) bildeten Untersuchungen zur Struktur von Porphyrinen (Kapitel 5) und beta-Carotin (Kapitel 6) als Vertreter wichtiger Klassen von Biomolekülen den Schwerpunkt dieser Arbeit. Die spektroskopischen Ergebnisse wurden durchweg über Strukturen und Schwingungsspektren, welche mit Hilfe der Dichtefunktionaltheorie (DFT) berechnet wurden, unterstützt. Die dritte bearbeitete Thematik zum Nachweis anthropogener und ökologisch relevanter Aerosole war bioanalytisch motiviert und wurde anhand von Pestizid-Modellsubstanzen bearbeitet (Kapitel 7).
The present studies which have been performed in the work-group C-2 (Prof. W. Kiefer) within the program of the Sonderforschungsbereichs 347, deal with the FT-Raman and –IR spectroscopy on new organometallic complexes, synthesized in the work-groups B-2 (Prof. W. Malisch), B-3 (Prof. W. A. Schenk), D-1 (Prof. H. Werner) and D-4 (Prof. D. Stalke). The FT-Raman spectra recorded at 1064 nm led to very useful and interesting information. Furthermore, the DFT calculations which are known to offer promise of obtaining accurate vibrational wavenumbers, were successfully used for the assignment of the vibrational spectra. For the first time it has been possible to ascribe exactly the n(RhC) stretching mode in the vinylidene rhodium(I) complex trans-[RhF(=C=CH2)(PiPr3)2] by using isotopic substitution, in conjunction with theoretical calculations. This is also true for the complexes trans-[RhF(CO)(PiPr3)2], trans-[RhF(C2H4)(PiPr3)2], trans-[RhX(=C=CHPh)(PiPr3)2] (X = F, Cl, Br, I, Me, PhCºC) and trans-[RhX(CN-2,6-xylyl)(PiPr3)2] (X = F, Cl, Br, I, CºCPh). In addition, the comparison between the n(RhC) wavenumbers of the complexes trans-[RhF(=13C=13CH2)(PiPr3)2] and trans-[RhF(CO)(PiPr3)2], containing the isoelectronic ligands 13C=13CH2 and CO, which have the same reduced mass, indicated that the Rh-C bond is stronger in the carbonyl than in the vinylidene complex. Besides, the n(RhF) stretching mode, which has been observed at higher wavenumbers in the FT-Raman and -IR spectra of trans-[RhF(CO)(PiPr3)2], showed that the carbonyl ligand is a better p-acceptor and a less effective s-donor than the vinylidene one. Moreover, the comparison of the n(CºC) and n(Rh-C) modes from the FT-Raman spectrum of the complexes trans-[Rh(CºCPh)(L)(PiPr3)2] (L = C=CHPh, CO, CN-2,6-xylyl) point out that the p-acceptor ability of the ligand trans to CºCPh should rise in the order C=CH2 < CO < CN-2,6-xylyl £ C=CHPh. The investigated sensitivity of the n(RhC), n(CC), n(CO) and n(CN) vibrational modes to the electronic modifications occuring in the vinylidene, carbonyl, ethylene and isonitrile complexes, should allow in the future the examination of the p-acceptor or p-donor properties of further ligands. Likewise, we were able to characterize the influence of various X ligands on the RhC bond by using the n(RhC) stretching mode as a probe for the weakening of this. The calculated wavenumbers of the n(RhC) for the vinylidene complexes trans-[RhX(=C=CHR)(PiPr3)2], where R = H or Ph, suggested that the strength of the Rh=C bond increases along the sequence X = CºCPh < CH3 < I < Br < Cl < F. For the series of carbonyl compounds trans-[RhX(CO)(PiPr3)2], where X = F, Cl, Br and I, analogous results have been obtained and confirmed from the model compounds trans-[RhX(CO)(PMe3)2]. Since, the calculated vibrational modes for the ethylene complex trans-[RhF(C2H4)(PiPr3)2] were in good agreement with the experimental results and supported the description of this complex as a metallacyclopropane, we were interested in getting more information upon this class of compounds. In this context, we have recorded the FT-Raman and -IR spectra of the thioaldehyde complexes mer-[W(CO)3(dmpe)(h2-S=CH2)] and mer-[W(CO)3(dmpe)(h2-S=CD2)] which have been synthezised by B-3. The positions of the different WL vibrational modes anticipated by the DFT calculations, were consistent with the experimental results. Indeed, the analysis of the band shifts in the FT-Raman and –IR spectra of the isotopomer mer-[W(CO)3(dmpe)(h2-S=CD2)] confirmed our assignment. The different stereoisomers of complex mer-[W(CO)3(dmpe)(h2-S=CH2)] were investigated too, since RMN and IR-data have shown that complex mer-[W(CO)3(dmpe)(h2-S=CH2)] lead in solution to an equilibrium. Since the information on the vibrational spectra of the molybdenum and tungsten complexes Cp(CO)2M-PR2-X (M = Mo, W; R = Me, tBu, Ph; X = S, Se) is very scarce, we extended our research work to this class of compounds. We have tried to elucidate the bonding properties in these chalcogenoheterocycle complexes by taking advantage of the mass effect on the different metal atoms (W vs. Mo). Thus, the observed band shifts allowed to assign most of the ML fundamental modes of these complexes. This project and the following one were a cooperation within the work-group B-2. The Raman and IR spectra of the matrix isolated photoproducts expected by the UV irradiation of the iron silyl complex Cp(CO)2FeSiH2CH3 have been already reported by Claudia Fickert and Volker Nagel in their PhD-thesis. Since no exact assignment was feasible for these spectra, we were interested in the study of the reaction products created by irradiation of the carbonyl iron silyl complex Cp(CO)2FeCH2SiH3. Although the calculated characteristic vibrational modes of the metal ligand unit for the various photoproducts are significantly different in constitution, they are very similar in wavenumbers, which did not simplify their identification. However, the theoretical results have been found to be consistent with the earlier experimental results. Finally, the last part of this thesis has been devoted to the (2-Py)2E- anions which exhibit a high selectivity toward metal-coordination. All di(2-pyridyl) amides and -phosphides which were synthesized by D-4, coordinate the R2Al+ fragment via both ring nitrogen atoms. This already suggests that the charge density in the anions is coupled into the rings and accumulated at the ring nitrogen atoms, but the Lewis basicity of the central nitrogen atom in Et2Al(2-Py)2N is still high enough to coordinate a second equivalent AlEt3 to form the Lewis acid base adduct Et2Al(2-Py)2NAlEt3. Due to the higher electronegativity of the central nitrogen atom in Me2Al(2-Py)2N, Et2Al(2-Py)2N and Et2Al(2-Py)2NAlEt3, compared to the bridging two coordinated phosphorus atom in Me2Al(2-Py)2P and Et2Al(2-Py)2P, the di(2-pyridyl)amide is the hardest Lewis base. In the phosphides merely all charge density couples into the rings leaving the central phosphorus atom only attractive for soft metals. These results were confirmed by using DFT and MP2 calculations. Moreover, a similar behaviour has been observed and described for the benzothiazolyl complex [Me2Al{Py(Bth)P}], where complementary investigations are to be continued. The DFT calculations carried out on the model compounds analysed in these studies supply very accurate wavenumbers and molecular geometries, these being in excellent agreement with the experimental results obtained from the corresponding isolated complexes.
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 electronic dynamics plays in the mechanism of photochemical reactions and photobiological processes. In order to approach this complex problem, different strategies within the framework of time-resolved, four-wave mixing spectroscopy were developed that allowed for the dynamic as well as the energetic aspects of vibronic coupling in non-radiative transitions of polyatomic molecules to be addressed. This was achieved by utilizing the influence of optical as well as Raman resonances on four-wave mixing processes. These resonance effects on third-order, optical processes allow for a high selectivity to be attained with respect to the interrogation of specific aspects of molecular dynamics. The development of different strategies within the framework of time-resolved, four-wave mixing spectroscopy for addressing the problem of vibronic coupling began with the experiments on gaseous iodine. This simple, well investigated molecular system was chosen in order to unambiguously characterize the effect of Raman resonances on four-wave mixing processes. A time-resolved degenerative four-wave mixing (DFWM) experiment was carried out on gaseous iodine that allowed for the dynamics of coherent Stokes Raman scattering (CSRS) as well as a coherent anti-Stokes Raman scattering (CARS) to be observed parallel to the dynamics of a DFWM process at different spectral positions of the FWM signal. Here, the state-selectivity of these different FWM processes manifests itself in the vibrational wave packet dynamics on different electronic potentials of iodine. It could be shown that Raman resonances determine the selectivity with which these FWM processes prepare and interrogate nuclear dynamics in different electronic states. With the insight gained into the relevance of Raman resonant processes in FWM spectroscopy, an experimental scheme was devised that utilizes this effect to selectively interrogate the dynamics of a specific vibrational mode within a polyatomic molecule during a radiationless electronic transition. Here, a CARS process was employed to selectively probe specific vibrational modes of a molecular system by variably tuning the energy difference between the lasers involved in the CARS process to be in Raman resonance with the vibrational energy spacing of a particular vibrational mode. Using this aspect of a tunable resonance enhancement within a CARS scheme, this optical process was incorporated in a time-resolved pump-probe experiment as a mode-selective probe mechanism. This type of experimental configuration, that employs four pulsed laser fields, was classified as a pump-CARS scheme. Here, a laser pulse independent of the CARS process initiates the molecular dynamics that are interrogated selectively with respect to the vibrational mode of the system through the simultaneous interaction of the three pulsed fields involved in the CARS process. Time-resolution on a femtosecond timescale is achieved by introducing a time delay between the independent pump laser and the laser pulses of the CARS process. The experimental configuration of a pump-CARS scheme was applied to the study of the nuclear dynamics involved in the radiationless electronic transition between the first excited singlet state (S1) and the electronic ground state (S0) of all-trans-b-carotene. The mode-selective CARS probe allowed for the characteristic timescale with which specific vibrational modes are repopulated in the S0 state to be determined. From the varying repopulation times of specific vibrational modes, a mechanism with which the full set of vibrational states of the S0 potential are repopulated subsequent to the internal conversion process could be postulated. Most importantly, the form of nuclear motion that primarily funnels the population between the two electronic states could be identified as the C=C symmetric symmetric stretch mode in the polyene backbone of b-carotene. With this, the reaction coordinate of this radiationless electronic transition could be identified. The experiment shows, that the CARS probe is capable of determining the nuclear motion coupled to a radiationless electronic transition in complex polyatomic systems. The S1/S0 internal conversion process in b-carotene was further investigated with time-resolved transient gratings. Here, the energetic aspects of a non-adiabatic transition was addressed by determining the influence of the vibrational energy on the rate of this internal conversion. In order to compare the rate of internal conversion taking place out of vibrational ground state modes versus this transition initiating out of vibrationally hot modes, the strategy of shifting the probe mechanism in the transient grating scheme to spectral positions within and out of the red flank of the S1 absorption profile was pursued. The interrogation of different vibrational states was verified by determining the degree of vibrational cooling, taking place parallel to the internal conversion process. With this strategy, it could be shown that vibrationally hot states contribute to the internal conversion with a higher rate than vibrational ground state modes. In summary, different third-order, optical processes in the framework of time-resolved FWM were applied to the study of non-adiabatic dynamics in polyatomic molecules. By utilizing the effect of optical as well as Raman resonances on different FWM processes, it could be shown that third-order, time-resolved spectroscopy is a powerful tool for gaining insight into complex molecular dynamics such as vibronic coupling. The experiments presented in this work showed that the CARS process, as a mode-selective probe in time-resolved experiments, is capable of disentangling nuclear and electronic dynamics.
Die vorliegende Arbeit hat zum Ziel, das Antwortverhalten nichtlinearer Reaktionen auf zielgerichtete Störungen zu untersuchen. Dabei beschäftigt sie sich mit zwei nichtlinearen chemischen Sauerstoff-Oszillatoren. Bei den beiden nichtlinearen chemischen Reaktionen handelt es sich um den Polyacrylamid-Methylenblau-Sauerstoff- (PA-MBO) Oszillator und um die Kupfer(II)ionen katalysierte Oxidation von Ascorbinsäure durch Luftsauerstoff. Im ersten Fall wird durch selektive Belichtung des Reaktionsmediums die gebildete Geloberfläche durch ein computergenerirtes Muster kodiert. Die Systemantwort wird mit Hilfe einer CCD-Kamera aufgenommen und danach einer Analyse unterzogen. Die erhaltenen Ergebnisse werden anschließend durch eine Computersimulation verifiziert. Die zweite untersuchte Möglichkeit, das PA-MBO-System einer Störung zu unterwerfen, ist das Anlegen eines externen elektrischen Feldes. In einer speziell dafür entworfenen Anordnung bildet sich ein quasi-eindimensionales Turing-Muster. In dieser quasi-eindimensionalen Anordnung kann die Reaktion leicht elektrischen Strömen von bis zu 200 mA/cm2 ausgesetzt werden. Die experimentellen Daten werden anschließend der Karhunen-Loeve Zerlegung unterworfen, um die komplexe Dynamik der Systemantwort zu studieren. Die Oxidation von Ascorbinsäure durch Luftsauerstoff in Gegenwart von Kupfer(II)ionen, wird im CSTR durchgeführt. Dabei läßt sich das Phänomen der stochastischen Resonanz beobachten, wenn man die Flußrate sinusförmig moduliert und dieser Frequenz zusätzlich weißes Rauschen überlagert.
In der vorliegenden Arbeit wurden zwei spektroskopische Methoden (Raman- und Circulardichroismus-Spektroskopie) und die Kernspinresonanz zur Untersuchung der Sekundärstruktur von synthetischen Polypeptiden eingesetzt. Dabei wurden die Struktur-Funktions-Beziehungen der dritten extrazellulären Schleife des Gonadotropin-freisetzenden Rezeptors (GnRH-R) untersucht. Die spektroskopischen Ergebnisse belegten, dass die zuvor getroffene Aussage über eine vorhandene helikale Struktur revidiert werden musste. Die Strukturanalysen mit Hilfe der CD-, Raman- und 2D NMR-Experimente an zwei Serien von Polypeptiden lieferten Aussagen über die Sekundärstruktur. Insbesondere die Raman-Untersuchungen in Verbindung mit einer statistischen Datenanalyse lieferten detaillierte Information über subtile Konformationsänderungen, die einerseits durch die Addition und andererseits durch die Substitution einzelner Aminosäuren in den synthetischen Polypeptiden ausgelöst wurden. Anhand der ausgewählten Raman-Linien konnte nachgewiesen werden, dass sowohl die Änderungen der Polypeptidkettenlänge als auch die Änderung der Polypeptidsequenzen mit den beobachteten Intensitäten der Raman-Linien korreliert sind.
Ziel dieser Arbeit war es, die Möglichkeiten zur Verwendung des Auges bzw. der Augenvorderkammer als spektroskopische Zelle für nicht-invasive In-vivo-Messungen zu untersuchen. Dabei stand vor allem die Geräte-technische Umsetzung und die Entwicklung geeigneter Auswertestrategien im Vordergrund. In dieser Arbeit konnte gezeigt werden, dass die spektroskopische Untersuchung von Kammerwasser-Substanzen möglich ist. Durch den Einsatz der UV/VIS-Spektroskopie konnte Fluorescein in vivo bestimmt werden. Die Anwendung der NIR-Spektroskopie eignet sich vor allem zur Bestimmung von Glucose im Kammerwasser. Die Güte der Glucose-Bestimmung ist von verschiedenen Faktoren abhängig, wie z. B. dem verwendeten Gerät, den Parameter der Auswertung und der Temperatur. Für weitergehende Studien sollten daher die in dieser Arbeit aufgedeckten Probleme und Strategien beachtet werden.
In dieser Arbeit wurde die unimolekulare Dissoziations- und Rekombinations-Reaktion von Jodmolekülen untersucht, die in mikroporösen Porosil-Kristalliten eingelagert waren. Hierfür wurden sowohl experimentelle Pump-Probe-Experimente als auch theoretische Untersuchungen auf der Femtosekunden-Zeitskala durchgeführt. Die Idee, die diesen Experimenten zugrunde lag, bestand darin, zu erfahren, in welcher Weise und in welchem Maße die Struktur der Umgebung einen Einfluss auf die elementaren dynamischen Prozesse der Reaktion ausübt. Die hier untersuchten Systeme I$_2$ in DDR-, TON-, FER- und MFI-Porosilen sind Modellsysteme für komplexere Moleküle, eingelagert in einer mikroporösen kristallinen Umgebung.
The thesis consists of two major parts. The first part contains a theoretical-experimental study of confocal micro-Raman spectroscopy on hybrid polymer coatings and an application of this spectroscopic method on PDMS-membranes. The theoretical-experimental study includes the application of a model that describes the influence of the refraction effect on the focus length on confocal Raman experiments, and the development of a new model that additionally takes into account the effect of diffraction on the focus dimensions. A parallel comparison between these two theoretical approaches and experimental data has been also drawn and a better agreement between theory and experiment was observed, when both refraction and diffraction effects were considered. Further, confocal resonance micro-Raman spectroscopy has been applied to characterise the diffusion processes of pharmacologically relevant molecules (b-carotene dissolved in dimethylsulfoxide) through a polydimethylsiloxane (PDMS)-membrane. The diffusion rate as a function of the measurement depth and diffusion time as well as the concentration gradient under a steady flux have been determined. The measurements shown that the confocal micro-Raman technique is a powerful tool to investigate the kinetics of diffusion processes within a membrane before the steady state has been reached. The second part of the thesis contains infrared and Raman spectroscopic studies of copper and iron doped B2O3-Bi2O3 glass systems. These studies were performed to obtain specific data regarding their local structure and the role played by dopant ions on boron and bismuthate units. The changes of B2O3 and Bi2O3 structural units due to the relaxation of the amorphous structure, which was induced in these samples by the thermal treatment, were also evidenced.
The thesis contains two major parts. The first part deals with structural investigations on different coordination compounds performed by using infrared absorption and FT-Raman spectroscopy in combination with density functional theory calculations. In the first section of this part the starting materials Ph2P-N(H)SiMe3 and Ph3P=NSiMe3 and their corresponding [(MeSi)2NZnPh2P-NSiMe3]2 and Li(o-C6H4PPh2NSiMe3)]2·Et2O complexes have been investigated in order to determine the influence of the metal coordination on the P–N bond length. In the next section the vibrational spectra of four hexacoordinated silicon(IV) and germanium(IV) complexes with three symmetrical bidentate oxalato(2-) ligands have been elucidated. Kinetic investigations of the hydrolysis of two of them, one with silicon and another one with germanium, have been carried out at room temperature and at different pH values and it was observed that the hydrolysis reaction occurs only for the silicon compound, the fastest reaction taking place at acidic pH. In the last section of this part, the geometric configurations of some hexacoordinated silicon(IV) complexes with three unsymmetrical bidentate hydroximato(2-) ligands have been determined. The second part of the thesis contains vibrational investigations of some biologically active molecules performed by means of Raman spectroscopy together with theoretical simulations. The SER spectra of these molecules at different pH values have also been analysed and the adsorption behaviour on the metal surface as well as the influence of the pH on the molecule-substrate interaction have been established.
Die vorliegende Dissertation beschäftigt sich mit nichtlinearen Reaktions-Transport-Systemen, die in zweidimensionalen Medien chemische Wellen und propagierende Fronten ausbilden können. Grundlage dieser Art von räumlichen Mustern sind sogenannte erregbare Systeme. Ein Themengebiet der Arbeit umfasst die Untersuchung von Spiralwellen in der Belousov-Zhabotinsky-Reaktion (BZ-Reaktion). Ein weiterer Teilabschnitt behandelt die Wechselwirkung zwischen Polymersystemen und nichtlinearen chemischen Reaktionen. In den untersuchten, räumlich ausgedehnten Systemen spielt die Kopplung nichtlinearer chemischer Reaktionen an Transportprozesse eine wichtige Rolle. Die generischen Typen von chemischen Mustern sind Pulswellen in einer Raumdimension, kreisförmige Wellen und Spiralen in einem zweidimensionalen System und kugelschalen- bzw. schraubenförmige Wellen in drei Raumdimensionen. Auf theoretischer Basis werden Effekte von Spiralwellen bei Änderung der Erregbarkeit des Reaktionsmediums dargestellt.In der vorliegenden Arbeit ist es erstmals gelungen, eine Methode zu entwickeln, die es erlaubt die Erregbarkeit in der BZ-Reaktion sowie in einer Vielzahl weiterer nichtlinearer Reaktionen zu beeinflussen. Ein weiteres Themengebiet dieser Dissertation ist die Untersuchung von pH-Systeme in Hydrogelen. Dies sind hydrophile Gele, die ihr Volumen in wässrigen Lösungen verändern können. In der vorliegenden Arbeit wurden Gele auf der Basis von Acrylamid und Methacrylat als Copolymer verwendet und an die oben beschriebenen pH-Oszillatoren angekoppelt. Durch Polymerisation von Acrylamid zusammen mit Natriummethacrylat konnte ein mit einem pH-Oszillator beladenes Gel hergestellt werden, das nach Start der Reaktion durch eine kleine Menge Säure mit einer deutlichen Volumenkontraktion reagiert. Diese Kontraktion des Gels konnte ausgenutzt werden, um die chemische Energie eines pH-Reaktionssystems in eine mechanische Kraftwirkung umzuwandeln.
In dieser Arbeit werden Pflanzen, Pflanzengewebe, Pflanzenzellen und Mikro-organismen spektroskopisch untersucht und ihre Inhaltsstoffe unter minimaler Probenpräparation im biologischen Gewebe direkt lokalisiert und identifiziert. Unter den verfügbaren Schwingungs-spektroskopischen Methoden ist die Mikro-Raman-Spektroskopie für diese Fragestellungen besonders gut geeignet, da Wasser Raman-Spektren nur wenig beeinflusst. Daher kann mit Raman-spektroskopischen Methoden auch in stark wasserhaltigem Gewebe gemessen werden. Weiterhin erhält man mit der Mikro-Raman-Spektroskopie eine gute räumliche Auflösung im sub-µm-Bereich, wodurch es möglich ist, heterogene Proben zu untersuchen. Darüber hinaus kann die Mikro-Raman-Spektroskopie mit anderen Methoden, wie z. B. der oberflächenverstärkten Raman-Spektroskopie (SERS), kombiniert werden. In pflanzlichen Zellen liegt eine Vielzahl von Substanzen in geringen Konzentrationen vor. Aufgrund der niedrigen Quantenausbeute des Raman-Effekts treten vor allem Substanzen, die eine Resonanz-Verstärkung erfahren, in den Spektren hervor. Diese Substanzen, wie z. B. b-Carotin, können deshalb in geringen Konzentrationen detektiert werden. Der Schwerpunkt dieser Arbeit liegt in der Untersuchung von Sekundär-Metaboliten wie Alkaloiden, Lipiden oder Terpenen, die in der Pflanze agglomerieren. Neben der Identifikation von Inhaltsstoffen, können die Raman-Spektren von Pflanzen für die chemotaxonomische Klassifizierung mit Hilfe der hierarchischen Clusteranalyse verwendet werden. Die Identifizierung von Mikroorganismen auch in sehr geringen Mengen (Monolage, einzelne Zellen) ist mit der Mikro-Raman-Spektroskopie nur unter bestimmten Voraussetzungen durchführbar. Für weitergehende Untersuchungen wird hier die SERS-Sonde oder ein TERS-Aufbau verwendet werden.
This thesis is concerned with the development of an on-line in-situ device for a chemical characterisation of flowing aerosols. The thesis describes the principles and most important features of such a system, allowing also on-line measurements using Raman spectroscopy as a diagnostic technique An analysis of the effect of forced oscillations on the motion of the particle dispersed in a gas flow is given in Chapter 2. Also the most important particle parameters are introduced. A review of the particle/fluid interaction in laminar air flows and the response of the particle is presented. In Chapter 3 the behaviour of the particle under different external conditions (ion bombardment and electric fields) is extended. A brief review of the most important particle charging theories (diffusion, field, and alternating potential charging) shows, that the effect of the electrical properties (represented by the dielectric constant) of the particles affects the charging process. A non-contact method for particle charge measurement was also presented. In the second part of the chapter, the interaction between the electric field and the charged particle for the purpose of particle trapping is illustrated. The most common systems like the two or four ring electrodynamic balance and the quadrupole trap are pointed out. In Chapter 4 a short review of the possibility of using scattered light to study aerosol particles is presented. First, the conditions and the facilities of using the Mie theory for particle size and refractive index determination are mentioned, then some features concerning the classical treatment of the Raman effect are presented Supported by the theoretical considerations exposed in Chapter 2, 3, and 4 the construction and the tests of different devices are presented in Chapter 5. Following the goal of the thesis, first an overview of the used materials and methods for particle generation is presented. Then, the constructed charging devices are described (from the mechanical and electrical point of view) and compared by measuring the acquired charge on the particle. Charged particles can be trapped in different containers. Two types of axially symmetric electrodynamic balances (two ring or an extended four ring configuration) were presented. For a deeper understanding these systems were studied using analytic and numerical methods. Considering the presented purpose of the work another type of trapping system has been developed, namely the quadrupole trap. A similar theoretical characterisation (in term’s of Mathieu equation) as for the electrodynamic balance was presented pointing out some specific features of this system. The incoming particle stream will be focused to the centre of the system simultaneously also the applied DC and AC potential onto the tube electrodes, yields a stable trapping of one or more particles. Chapter 6 consists of two parts: the system for single particle and for many particles investigation. The individual devices presented in Chapter 5 are now put together. The first part presents the method and the experimental realisation of a set-up for solid particle injection. In order to suppress the phase injection disadvantage found for the electrodynamic balance a developed program processes the information obtained from a particle cloud through an adequate electronic detection system, and reduces the number of particles until just one single particle is trapped. The method for one particle investigation can be extended for many particles. Using the presented set-up the particles are moved from one quadrupole to another and transformed from a particle cloud to a particle stream. A linearity between an external vertical mounted detector and the formed image of the particle stream on the CCD camera has been observed and used for simultaneous detection of many particles by Raman spectroscopy. For both methods Raman results are presented. One limitation of Raman Spectroscopy is the relatively long integration time needed for adequate signal-to-noise ratio. There are two factors which influence the integration time: first the incident radiation and the detector sensitivity, and second the intensity of the Raman bands. Using a CCD detector, the desired detector sensitivity should be achieved. So, the improvement of the signal-to-noise ratio should be the next goal in the system development. In order to reduce the integration time an optical system including optic fibres and the integration of an FT-Raman module operating in the visible region is planed. The goal of this work was to develop and construct an instrument for on-line in-situ single particle investigation by Raman spectroscopy. With the presented experimental set-up and the developed program the purpose of the work, the on-line in-situ near atmospheric pressure aerosol investigation was achieved. The Raman spectroscopy has been used successfully for a chemical characterisation of the aerosol particles.
Untersuchungen an biologischen Proben mit verschiedenen Raman- und SERS-spektroskopischen Techniken
(2003)
Diese Arbeit befasst sich mit der Entwicklung und Erprobung geeigneter Methoden zur Raman-spektroskopischen Untersuchung empfindlicher, insbesondere biologischer Proben. Das Ziel dabei ist, ein Werkzeug zur Verfügung zu stellen, mit dem es möglich ist, detaillierte Informationen über die Inhaltsstoffe einer Probe und deren räumlichen Verteilung zu sammeln. Diese Daten sind beispielsweise für die Qualitätssicherung pharmazeutischer Produktionen notwendig. Zu diesem Zweck wurden zwei verschiedene Ansätze verfolgt: ein Raman-Spektrometer wurde zum einen mit einer Glasfasersonde, zum anderen mit einer optischen Gradientenfalle kombiniert. Beide Ansätze wurden getestet und mit ihnen biologische Fragestellungen bearbeitet. Die Empfindlichkeit biologischer Proben und die geringe Konzentration ihrer Inhaltsstoffe macht es dabei notwendig, besonderen Wert auf probenschonende Messverfahren und eine hohe Nachweisempfindlichkeit zu legen. Die Raman- bzw. SERS-Spektroskopie ist hierzu in der Lage und erfordert gleichzeitig nur eine minimale Probenpräparation. Anhand der präsentierten Experimente konnte gezeigt werden, dass sich die SERS-Glasfasersonde besonders zur Untersuchung empfindlicher Proben eignet. Insbesondere erlaubt sie minimal-invasives Arbeiten an biologischen Materialien. Es konnte außerdem gezeigt werden, dass die Sonde aufgrund ihrer geometrischen Beschaffenheit eine gute Ortsauflösung, bis in den Sub-Mikrometerbereich, bei den Messungen erlaubt. Daher eignet sich die Fasersonde besonders zur Untersuchung von hochempfindlichen biologischen Proben bei gleichzeitig sehr geringem Probenbedarf. Mit der optischen Gradientenfalle, als zweite Methode, hat man ein Werkzeug zur Hand, mit dem es möglich ist, einzelne Mikroorganismen oder Mikropartikel in Suspension zu vermessen. Bei Arbeit mit der optischen Gradientenfalle ist eine freie, dreidimensionale Manipulation der gefangenen Zellen im Probengefäß möglich. Auf diese Weise können einzelne Zellen über längere Zeit stabil im Laserfokus gehalten werden, wodurch längere Integrationszeiten möglich werden. Außerdem kann man auf diese Weise eine Immobilisierung der suspendierten Zellen auf einer funktionalisierten Oberfläche vermeiden, wodurch unerwünschte Effekte auf das zu messende Spektrum, wie z. B. Verschiebungen einzelner Banden oder Änderungen in den relativen Bandenintensitäten, ausgeschlossen werden können. Zur Untersuchung partikulärer Verunreinigungen ist es nicht notwendig, die Lösung aus dem Gefäß heraus zu präparieren. Vielmehr können die Mikropartikel durch die optische Gradientenfalle in der Lösung festgehalten und spektroskopisch identifiziert werden. Dies ermöglicht beispielsweise die Charakterisierung von Verunreinigungen in pharmazeutischen Lösungen, ohne dass dafür Ampullen geöffnet werden müssten. Auf diese Weise können Kontaminantien identifiziert werden, ohne Gefahr zu laufen, bei der Probenpräparation weitere Verunreinigungen zu verursachen und damit die Messungen zu verfälschen. Durch die Kombination eines Raman-mikroskopischen Aufbaus mit der SERS-Glasfasersonde bzw. der optischen Gradientenfalle ist es gelungen, Fragestellungen an biologischen Systemen in sehr Proben-schonender, aber gleichzeitig hoch-ortsauflösender Weise zu bearbeiten. Durch die Verwendung nicht-kontaminierender SERS-Sonden ist es möglich, zusätzliche Verstärkungseffekte zu erzielen. Die verwendeten Anregungslaserleistungen können daher generell niedrig gehalten werden. Dennoch erhält man aussagekräftige Spektren in einer akzeptablen Zeit. Die Zwei-Laser-Lösung für die optische Gradientenfalle stellt ein zuverlässiges Werkzeug zur berührungsfreien Manipulation kleiner Partikel bei gleichzeitiger Flexibilität in Bezug auf die Anregungswellenlänge dar.
In dieser Arbeit werden biologisch relevante Oberflächen untersucht, die in der Medizin bzw. in der Biologie eine wichtige Rolle spielen. Die Proteinadsorption auf Implantat-Oberflächen wurde charakterisiert, um wichtige Informationen über den Adsorptionsprozess zu erhalten. Das Fernziel hierbei ist, durch ein umfassendes Wissen über diesen für die Implantation wichtigen Schritt Biomaterialien mit möglichst hoher Gewebeverträglichkeit zu entwickeln. Die Verteilung von Propolis auf der Wachs-Oberfläche von Bienenwaben wurde untersucht, um mehr über dessen Nutzen, der noch nicht vollständig aufgeklärt ist, zu erfahren und um auf mögliche Auswirkungen einer veränderten Wabenstruktur auf die Kommunikation der Honigbienen Rückschlüsse ziehen zu können. Das Ziel des ersten Teils dieser Arbeit war, das Adsorptionsverhalten der Proteine Fibrinogen, Albumin und Fibronektin auf Titandioxid, einem in der Medizin häufig als Implantat eingesetzten Material, zu studieren. Die Adsorption von Proteinen auf der Oberfläche von Implantaten ist ein wichtiger Schritt für die Gewebeverträglichkeit bzw. Biokompatibilität dieser Materialien. Es wurden sowohl die räumliche Verteilung der Proteine auf den Implantat-Oberflächen als auch die durch die Adsorption hervorgerufenen strukturellen Veränderungen der Proteine untersucht. Als Methoden wurden hierfür die Laser-Raster-Mikroskopie (LSM), die Kraftfeldmikroskopie (AFM) sowie die Raman-Spektroskopie eingesetzt. Durch ein umfassendes Wissen über den Adsorptionsprozess der Proteine auf Implantat-Materialien können die Oberflächen der Implantate dahingehend verändert werden, dass es zu einer besseren Proteinadsorption und dadurch zu einer noch geringeren Rate an Abstoßungsreaktionen kommt. Die in dieser Arbeit vorgestellten Ergebnisse können einen Teil zum Verständnis des Adsorptionsprozesses beitragen. Das Ziel des zweiten Teils dieser Arbeit war es, die chemische Zusammensetzung von Propolis (dem Kittharz der Bienen) und Wabenwachs von Apis mellifera carnica Pollm. sowie die räumliche Verteilung von Propolis auf den Waben-Oberflächen zu untersuchen. Hierzu wurden die Raman-Spektroskopie und Raman-Mapping eingesetzt. Es wurden zunächst Raman-Spektren von Propolis-Proben sowie Raman-Spektren von charakteristischen Standardsubstanzen des Propolis aufgenommen. Das Propolis-Spektrum sowie das Wachs-Spektrum wurden durch eine Auswahl an Standardsubstanzen simuliert. Um herauszufinden, welche Harze von den Bienen gesammelt und als Propolis im Stock verwendet werden, wurden von einigen Harzen, die als Propolis-Quellen in Betracht kommen, Raman-Spektren aufgenommen. Es wurde auch analysiert, ob die Kettenlängen der Alkane, aus denen die Wachse bestehen, einen Einfluss auf die Raman-Spektren hat. Mittels Raman-Mapping wurde schließlich die räumliche Verteilung von Propolis auf der Waben-Oberfläche untersucht. Die hier charakterisierten biologisch relevanten Oberflächen spielen eine wichtige Rolle in der Medizin und in der Biologie. Die Analyse mit mikroskopischen und spektroskopischen Methoden verschafft einen Einblick in die Prozesse, die sich an diesen Oberflächen abspielen. Die Proteinadsorption auf Implantat-Oberflächen sind für die Implantationsmedizin von Bedeutung. Es werden ständig neue Materialien entwickelt, die eine möglichst gute Biokompatibilität aufweisen sollen. Erkenntnisse über die Prozesse, die hierfür eine Rolle spielen, helfen bei der Entwicklung neuer Materialien. Die Verteilung von Propolis auf den Wachs-Oberflächen hat einen Einfluss auf die Materialbeschaffenheit der Waben. Dies könnte die Vibrationsweiterleitung beim Schwänzeltanz der Honigbienen, der für deren Kommunikation von Bedeutung ist, beeinflussen. Die Verteilung des Propolis auf den Waben konnte für kleine Ausschnitte gezeigt werden. Inwiefern eine Propolisschicht auf den Stegen der Waben die Vibrationsweiterleitung tatsächlich beeinflusst, muss durch weiterführende Experimente herausgefunden werden.
In the current work, several well-known pharmaceuticals (1,4-dihydrazinophthalazine sulfate, caffeine, and papaverine hydrochloride) and new organometallic compounds (nickel(II) cupferronato complexes NiL2An, L = PhN2O2-, n = 1, A = o-phenanthroline (1), o,o’-bipyridine (2) and n = 2, A = H2O (3), o-NH2Py (4), o-C6H4(NH2)2 (5); silylene-bridged dinuclear iron complexes [Cp(OC)2Fe]2SiX2 (X = H (6), F (7), Cl (8), Br (9), I (10)); 3-silaoxetane 3,3-dimethyl-2,2,4,4-tetraphenyl-1-oxa-3-silacyclobutane (11) and 3-silathietane 3,3-dimethyl-2,2,4,4-tetraphenyl-1-sila-3-thiacyclobutane (12) compounds), which have successfully been characterized by using vibrational spectroscopy in conjunction with accurate density functional theory (DFT) calculations, are presented. The DFT computed molecular geometries of the species of interest reproduced the crystal structure data very well and in conjunction with IR and Raman measurements helped us to clarify the structures of the compounds, for which no experimental data were available; and this, especially for the new organometallic compounds, where the X-Ray analysis was limited by the non-availability of single crystals (3, 5, 10). Furthermore, a natural population analysis (NPA) and natural bond orbital (NBO) calculations together with a detailed analysis of the IR and Raman experimental as well as calculated spectra of the new organometallic compounds, allowed us to study some special bonding situations (1-12) or to monitor the structural changes observed with the change in temperature during the Raman experiments (11, 12). By combining these two methods (DFT and vibrational spectroscopy), the auspicious results obtained on the organometallic compounds 6-12 and overall in literature, made us confident of the power of theoretical calculations in aiding the interpretation of rich SERS spectra by solving some interesting issues. Consequently, the Raman and SERS spectra of well-known pharmaceuticals (1,4-dihydrazinophthalazine sulfate, caffeine, and papaverine hydrochloride) or new potentially biological active organometallic complexes (1-5), that were synthetized by our coworkers, were discussed with the assistance of the accurate results obtained from DFT calculations (structural parameters, harmonic vibrational wavenumbers, Raman scattering activities), and many previous incomplete assignments have been analyzed and improved. This allowed us to establish the vibrational behavior of these biological compounds near a biological artificial model at different pH values or concentrations (Ag substrate), taking into account that information about the species present under particular conditions could be of great importance for the interpretation of biochemical processes. The total electron density of molecules and the partial charges situated on selected atoms, which were determined theoretically by NPA, allowed us to establish the probability of different atoms acting as an adsorptive site for the metal surface. Moreover, a closer examination of the calculated orbitals of molecules brought further arguments on the presence or absence of the photoproducts at the Ag surface during the irradiation (1,4-dihydrazinophthalazine sulfate). Overall, the results provide a benchmark illustration of the virtues of DFT in aiding the interpretation of rich vibrational spectra attainable for larger polyatomic adsorbates by using SERS, as well as in furnishing detailed insight into the relation between the vibrational properties and the nature of the Ag substrate-adsorbate bonding. Therefore, we strongly believe that theoretical calculations will become a matter of rapidly growing scientific and practical interest in SERS.
Die Untersuchung der molekularen Dynamik elektronisch angeregter Moleküle stand im Zentrum dieser Arbeit. In vielen Fällen ist die Dynamik dieser Zustände mit einer Bewegung von Wasserstoffatomen assoziiert. Mittels zeit- und frequenzaufgelöster Photofragmentspektroskopie lassen sich Aussagen über die Energieumverteilung während der Dissoziation und über die Geschwindigkeit der Wasserstoffatomabstraktion treffen. Die Ergebnisse solcher Messungen können als Grundlage für die Diskussion der molekularen Reaktionsdynamik und als Prüfstein für theoretische Berechnungen dienen. Theoretische Vorhersagen weisen der Wasserstoffatomdynamik eine enorme Bedeutung für die Photochemie von Biomolekülen zu. Unter den Biomolekülen nimmt die Untersuchung der Photochemie und der Photophysik isolierter DNA-Basen eine herausragende Stellung ein. Diese Untersuchungen sind dabei stark von der Hoffnung auf ein besseres Verständnis der Entstehung von Strahlungsschäden motiviert, die letztendlich zu Hautkrebs führen können. Die Frage, ob jeder Baustein der DNA potentiell photostabil ist, wurde im Rahmen dieser Arbeit für die DNA-Base Adenin untersucht. Die Experimente erfolgten an isolierten Molekülen in der Gasphase, so dass es möglich war, die intrinsischen Eigenschaften von Adenin zu untersuchen. Es konnte dabei gezeigt werden, dass Adenin nach Bestrahlung mit UV-Licht vornehmlich das N9-H-Wasserstoffatom abspaltet und diese Abspaltung extrem schnell verläuft. Dies steht in Einklang mit einem Deaktivierungsprozess über eine repulsive Potentialkurve, wie er theoretisch vorhergesagt worden war. In natürlicher Umgebung, d.h. in wässriger Lösung, sind Wasserstoffatome, die in der Gasphase unter UV-Stress abdissoziieren, in Wasserstoffbrückenbindungen zu Solvensmolekülen oder in das Makromolekül eingebunden. Daher kann Bestrahlung zu Wasserstoffatom- oder Protonentransfer führen. Die Frage, ob nach UV-Anregung photoacide Verbindungen wie Phenol oder Naphthol ein Wasserstoffatom oder ein Proton an Solvensmoleküle übergeben, steht derzeit im Mittelpunkt lebhafter wissenschaftlicher Diskussion. Für das Verständnis der Photoacidität ist die Kenntnis der Schwingungsstruktur, v.a. der intermolekularen Schwingungen, von Phenol- bzw. Naphthol-Wasser-Clustern unerlässlich. Für den Naphthol/(H2O)1-Cluster konnten für den ersten elektronisch angeregten Zustand alle intermolekularen in plane Schwingungen nachgewiesen werden. Wasserstoffatomdynamik ist nicht nur für geschlossenschalige Biomoleküle wie Adenin oder wasserstoffbrückengebundene Cluster von Bedeutung, sondern auch für offenschalige organische Radikale. Alkylradikale sind dabei als reaktive Intermediate u.a. in chemischenVerbrennungsprozessen äußerst wichtig. Für das hier untersuchte tert-Butylradikal konnte ein Wasserstoffverlust beobachtet werden. Dieser verlief bei niedrigen Anregungsenergien gemäß statistischer Vorhersagen, bei höheren Anregungsenergien jedoch deutlich langsamer als aus einfachen statistischen Modellen zu erwarten wäre. Diese Ergebnisse könnten sich mit einem bisher nicht identifizierten elektronischen Zustand erklären lassen, der eine Rolle in der Photochemie bzw. Photodissoziationsdynamik spielt und möglicherweise von allgemeiner Bedeutung für die Photophysik von Alkylradikalen ist. Zukünftige Arbeiten werden die Untersuchungen der Wasserstoffatomdynamik der im Rahmen dieser Arbeit untersuchten Systeme vertiefen und auf weitere relevante Moleküle (Thymin, Cytosin, Guanin, Uracil, primäre und sekundäre Alkylradikale) ausdehnen.
Subject of this work was to investigate the influence of nonadiabatic coupling on the dynamical changes of electron and nuclear density. The properties of electron density have neither been discussed in the stationary case, nor for excited electronic states or for a coupled electronic and nuclear motion. In order to remove these restrictions one must describe the quantum mechanical motion of all particles in a system at the same level. This is only possible for very small systems. A model system developed by Shin and Metiu [1, 2] contains all necessary physical ingredients to describe a combined electronic and nuclear motion. It consists of a single nuclear and electronic degree of freedom and the particle interaction is parameterized in such a way as to allow for a facile switching between and adiabatic (Born-Oppenheimer type) and a strongly coupled dynamics. The first part of the work determined the “static” properties of the model system: The calculation of electronic eigenfunctions, adiabatic potential curves, kinetic coupling elements and transition dipole moments allowed for a prediction of the coupled dynamics. The potentials obtained from different parameterization showed two distinct cases: In the first case the ground and first excited state are separated by a large energy gap which is the typical Born-Oppenheimer case; the second one exhibits an avoided crossing which results in a breakdown of the adiabatic approximation. Due to the electronic properties of the system, the quantum dynamics in the two distinct situations is very different. This was illustrated by calculating nuclear and electron densities as a function of time. In the Born-Oppenheimer case, the electron density followed the vibrational motion of the nucleus. This was demonstrated in two examples. In the strongly coupled case the wave packet did not exhibit features caused by nonadiabatic coupling. However, projections of the wave function onto the electronic states revealed the usual picture obtained from solutions of the nuclear Schrödinger equation involving coupled electronic states. In that case the nuclear motion triggered charge transfer via nonadiabatic coupling. The second part of the work demonstrated that the model system can easily be modified to yield binding situations often found in diatomic molecules. The different situations can be characterized in terms of bound and dissociative adiabatic potential curves. The investigation focussed on the case of an electronic predissociation, where the ground state is dissociative in the asymptotic limit of large internuclear distances. Within our model system we were able to demonstrate how the character of the electron density changes during the fragmentation process. In the third part we investigated the influence of external fields on the correlated dynamics of electron and nucleus. Employing adiabatic potential curves, the structure of absorption spectra can be understood within the weak-field limit. In the above described Born-Oppenheimer case the adiabatically calculated spectrum was in very good agreement with the exact one, whereas in the strongly coupled case the obtained spectrum was not able to resemble the exact one. Regarding the dynamics during a laser excitation process the time-dependent electron and nuclear densities nicely illustrated the famous Franck-Condon principle. The interaction with strong laser pulses lead to an excitation of many bound electronic and vibrational states. The electron density reflected the classical-like quiver motion of the electron induced by the fast variations of the electric field. The nucleus did not follow these fast oscillations because of its much larger mass. The last part of the work extended the original model system by including an additional electron. As a consequence of the Pauli principle, the spatial electronic wave function has to be either symmetric or anti-symmetric with respect to exchange of the two electrons. This corresponds to anti-parallel or parallel electron spins, respectively. The extended model already contains the physical properties of a many-electron system. Solving the time-dependent Schrödinger equation for a typical vibrational wave packet motion clearly indicated that the electron density is no longer suited to “localize” single electrons. We extended the definition of the electron localization function (ELF) to an exact, time-dependent wave function and demonstrated, how the ELF can be used to further characterize a coupled electron and nuclear motion. Finally, we gave an outlook of how to define electron localization in the case of anti-parallel electron spins. We derived a quantity similar to the ELF denoted “anti-parallel spin electron localization function” (ALF) and demonstrated that the ALF allows to follow time-dependent changes of the electron localization in a numerical example. [1] S. Shin, H. Metiu, J. Chem. Phys. 1995, 102, 9285. [2] S. Shin, H. Metiu, J. Phys. Chem. 1996, 100, 7867.
The present work consist of two major parts. The first part, extending over chapters 1, 2, 3 and 4, addresses the design and construction of a device capable of determining the shell thickness and the core size for monolayer spherical particles in a flow. The second part containing chapters 5, 6, 7, 8, 9 and 10, concentrate on the use of Raman spectroscopy as a space application, namely for use as a tool for in situ planetary investigations. This part directly addresses the MIRAS project, a study run under the auspices of Federal Ministry of Education and Research, BMBF and German Aerospace Center, DLR under national registration number 50OW0103. MIRAS stands for "Mineral Investigation by in situ Raman Spectroscopy". Microcapsule Sizing by Elastic Light Scattering The industrial development of processes based on microcapsules depends on the possibility to provide clear and complete information about the properties of these microcapsules. However, the tools for an easy and efficient determination of the microcapsule properties are lacking, several methods being often required to describe adequately the microcapsule behavior. Methods for evaluating the individual size and size distribution of both the core and the shell are required together with methods for measuring the mechanical strength, stability in appli-cation media, permeability of the shell, etc. Elastic light scattering measurements provide a possible way of determining properties such as core size, shell size and refractive index. The design and con-struction of a device capable of measuring the above mentioned parameters for a core-shell particle is the subject of the first part of this thesis. The basic principle of measurement for the device proposed here consists of an-alyzing one particle at a time by recording the elastic light scattering pattern at angles between approx. 60 and 120 grad. By comparing the experimentally recorded phase functions with the previously calculated phase functions stored in a database, the geometry of the scattering object can be identified. In our case the geometry is characterized by two parameters: the shell thickness and the core radius. In chapter 2 a short overview on the methods used for sizing microparticles is given. Different sizing methods are compared, and the advantages and disadvan-tages for the general problem of sizing are shortly discussed. It is observed that all sizing methods that are based on elastic light scattering theories are ensemble methods. Chapter 3 focusses on the theories used for calculating the theoretical scattering patterns with emphasize on the Mie theory. The generalization of Mie theory for layered particles is shortly presented and the far field intensity approximations are discussed. The last chapter (4) of this first part describes the experimental approach for building an automatic microcapsule sizer. The approach started by O. Sbanski [76] with the development of a software packet for calculating and storing theoret-ical phase functions for core-shell particles was continued with the designing and construction of a measuring device. The hardware construction and the software with all implemented corrections imposed by the individual setup components are described in detail. For the laser, the monochromaticity, the intensity profile of the beam as well as the planarity of the equi-phase fronts are taken into consid-eration. The flow cell with three different designs is described, and the influences of the employed design on the light scattering patterns are discussed together with the optical system used for recording the experimental phase functions. The detection system formed by two identical linear CCD arrays is presented together with the software approach used for data acquisition. Ways of improving the quality and the speed of the analyzing process are discussed. The final section presents measurements run on samples made of homogeneous spheres and also on samples containing industrial microcapsules. Mineral Investigation by in situ Raman Spectroscopy The envisaged future planetary missions require space-born instruments, which are highly miniaturized with respect to volume and mass and which have low needs of power. A micro Raman spectrometer as a stand alone device on a planetary surface (e.g. Mars) offers a wide spectrum of possibilities. It can assess the chemical analysis via determination of the mineral composition, detect organic molecules in the soil, identify the principal mineral phases, etc. The technical developments in the last years have introduced a new generation of small Raman systems suitable for robotic mineral characterization on planetary surfaces [20, 95]. Two different types of spectrometer were considered for the MIRAS study. As supporting laboratory experiments for the MIRAS study, the measure-ments on standard minerals and on SNC Mars meteorites are discussed in chapter 6. The following SNC meteorites have been investigated: Sayh al Uhaymir 060, Dar al Gani 735, Dar al Gani 476, Northwest Africa 856, Los Angeles, Northwest Africa 1068 and Zagami. Pyrite as a hitherto undescribed phase in the picritic (olivin-phyric) shergottite NWA 1068 as well as reduced carbon (e.g. graphite) and anatase in the shergottite Say al Uhaymir 060 are new findings for this class of meteorites. A detailed description of the proposed designs for MIRAS, with the compo-nents used for building the test version on a breadboard is covered in chapter 7. The scientific as well as the mission requirements imposed on the instrument are discussed. The basic design is presented and the main components that are brought together to build the device being the laser unit, the Raman head, the Rayleigh filtering box, and the spectral sensor (spectrometer with a matching de-tector) are described. The two proposed designs, one based on an acousto-optic tunable filter (AOTF) and the other based on a dispersive hadamard transform spectrometer are compared to each other. The actual breadboard setup with the detailed description of the components follows in Section 7.3. Further de-velopment of a Raman spectrometer for planetary investigations is proposed in combination with a microscope as part of the Extended-MIRAS project. The software developed for controlling the breadboard version of MIRAS is described in chapter 8 together with a short description of the structure of a relational database used for in house spectra management. The measuring pro-cedures and the data processing steps are presented. Spectra acquired with the MIRAS breadboard version based on the AOTF are shown in chapter 9. The final chapter addresses a rather different possibility of using Raman spectroscopy for planetary investigations. The chapter summarizes the content of four tech-nical notes that were established within the study contracted by the European Space Agency with firma Kayser-Threde in Munich concerning the possibility of applying Raman spectroscopy in the field of remote imaging.
The present thesis reports about vibrational and quantum chemical investigations on model systems undergoing photochemical processes and pharmaceutically active compounds, respectively. Infrared (IR) and Raman spectroscopy were applied for the characterization of the ground state molecular structure. Moreover, resonance Raman (RR) spectra contain additional information about the resonantly enhanced excited state molecular structure. A quantitative resonance Raman intensity analysis in conjunction with the simultaneous simulation of the absorption spectra by means of time-dependent propagation methods was accomplished in order to extract valuable information about the excited state molecular structures of the investigated systems. Surface enhanced Raman scattering (SERS) allows one to determine the interaction and adsorption site of active agents on a metal substrate. Furthermore, density functional theory (DFT) and potential energy distribution (PED) calculations were carried out for an exact assignment of the vibrational spectra. Complete active space self consistent field (CASSCF) and configuration interaction (CI) calculations for some model systems were also performed to assess the experimental results on the excited state potential surfaces. The fundamentals of resonance Raman spectroscopy are treated in detail, describing the physical processes and emphasizing the theoretical methodologies which allow one to obtain the information about the resonantly excited state via an RR intensity analysis. The Brownian oscillator model to determine the solvent reorganization energy is briefly presented. Furthermore, the SERS enhancement mechanisms and selection rules to determine the orientation of the molecules adsorbed on the metal substrate are discussed. The Hartree-Fock approach to calculate the ground state geometry is expatiated, and the basic characteristics of the CI and CASSCF calculations are specified. The chapter ends with a short description of the DFT calculations. Chapter 4 deals with the investigation of the excited state intramolecular proton transfer of the model system, 1-hydroxy-2-acetonaphthone (HAN). The vibrations showing the highest displacement parameters correspond to stretching and in-plane deformation modes of the naphthalene ring and the conjugated carbonyl group, while the OH stretching mode exhibits no observable enhancement. The cooperative effect of the skeletal vibrations reduces the distance between the carbonyl and hydroxyl oxygen atoms in accordance with a general electron density redistribution. Hence, the leading force in the proton transfer process is the increase in electron density on the carbonyl group and the decrease of the negative charge on the hydroxyl oxygen. In chapter 5 the structural and vibrational characteristics of the organic mixed valence system N,N,N’,N’-tetraphenylphenylenediamine radical cation (1+) are discussed. The resonance Raman measurements showed that at least eight vibrational modes are strongly coupled to the optical charge transfer process in (1+). These Franck-Condon active modes were assigned to symmetric vibrations. The most enhanced band corresponds to the symmetric stretching mode along the N-phenylene-N unit and exhibits the largest vibrational reorganization energy. Nevertheless, symmetric stretching modes of the phenylene and phenyl units as well as deformation modes are also coupled to the electronic process. The total vibrational reorganization energy of these symmetrical modes is dominant, while the solvent induced broadening and reorganization energy are found to be small. Hence, (1+) adopts a symmetrical delocalized Robin-Day Class III structure in the ground state. Chapter 6 reports about a vibrational spectroscopic investigation of a model organic photorefractive thiophene derivative, 2-(N,N-diethylamino)-5-(2’,2’-dicyanovinyl)-thiophene. The geometry of the first excited state were optimized and the FC parameters were calculated using the configuration interaction with single excitations method. These calculations show that the contribution of the zwitterionic structure to the excited state is significantly higher than in the ground state. The resonance Raman spectra indicate that several stretching modes along the bonds connecting the donor and acceptor moieties as well as the S-C stretching vibrations are enhanced. Chapter 7 presents the vibrational analysis of an aziridinyl tripeptide, a cysteine protease inhibitor active drug. The vibrational analysis reveals stronger H-bonding of the aziridine NH unit in the solid state of the aziridinyl tripeptide than in the liquid electrophilic building block, indicating medium strong intermolecular H-bond interactions in the crystal unit. The amide hydrogen atoms of the aziridinyl tripeptide are involved in weaker H-bonds than in an epoxide analogon. Furthermore, the characteristic vibrational modes of the peptide backbone were discussed. Chapter 8 reports on the adsorption mechanism of two related anti-leukemia active agents, 6-mercaptopurine (6MP) and 6-mercaptopurine-ribose (6MPR) on a silver colloid. Both molecules adsorb through the N1 and possibly S atom on the metal surface under basic conditions. The SERS spectra recorded for acidic pH values showed that the ribose derivative exhibits a different adsorption behavior compared to the free base. 6MP probably adsorbs on the silver sol through the N9 and N3 atoms, while 6MPR interacts with the surface via the N7 and probably S atoms. Around critical biological concentrations and pH values i.e. at low concentrations and almost neutral condition (pH 7-9), 6MPR interacts with the substrate through both N7 and N1 atoms, possibly forming two differently adsorbed species, while for 6MP only the species adsorbed via N1 was evidenced.
In the experiments presented in this work, linear and non-linear femtosecond time-resolved spectrsocopy were applied to investigate the structure-function and functiondynamics relationship in biological and artificially designed systems. The experiments presented in this work utilize femtosecond time-resolved transient absorption and transient grating as well as picosecond time-resolved fluorescence spectroscopy to investigate the photophysics and photochemistry of biological photoreceptors and address the light-induced excited-state processes in a particular molecular device that serves as a - structurally - very simple light-harvesting antenna and potentially as a catalysis-switch for the production of hydrogen in solution. The combination of white-light probe transient absorption and coherent transient grating spectroscopies yields spectral information about the excited state absorption in concert with high quality, high signal-to-noise kinetic transients, which allow for precise fitting and therefore very accurate time-constants to be extracted from the data. The use of femtosecond time-resolved transient grating spectroscopy is relatively uncommon in addressing questions concerning the excited-state reaction pathways of complex (biological) systems, and therefore the experiments presented in this work constitute according to the literature the first studies applying this technique to a a metalloporphyrin and an artificial light-harvesting antenna.