Refine
Year of publication
Document Type
- Doctoral Thesis (130)
- Article (97)
- Conference Proceeding (17)
Language
- English (244) (remove)
Has Fulltext
- yes (244)
Is part of the Bibliography
- no (244)
Keywords
- - (79)
- Plasma (23)
- Plasmaphysik (22)
- Stellarator (13)
- Plasmadiagnostik (10)
- Komplexes Plasma (7)
- Wendelstein 7-X (7)
- Cluster (6)
- Kernfusion (6)
- dusty plasma (6)
- Ionenfalle (5)
- Metallcluster (5)
- barrier discharge (5)
- Atmosphärendruckplasma (4)
- Divertor (4)
- Fusion (4)
- Fusionsplasma (4)
- Hochfrequenzplasma (4)
- Massenspektrometrie (4)
- Modellierung (4)
- Penningfalle (4)
- Physik (4)
- Plasmachemie (4)
- Polyanion (4)
- Simulation (4)
- Spektroskopie (4)
- magnetron sputtering (4)
- plasma (4)
- stellarator (4)
- surface charge (4)
- 52.70.Ds (3)
- Absorptionsspektroskopie (3)
- Aluminium (3)
- Clusterion (3)
- Dissertation (3)
- Festkörperphysik (3)
- Flugzeitspektrometrie (3)
- Gasentladung (3)
- Kernphysik (3)
- Laserinduzierte Fluoreszenz (3)
- Laserspektroskopie (3)
- Niedertemperaturplasma (3)
- Penning trap (3)
- Plasma Physics (3)
- Plasma-Wand-Wechselwirkung (3)
- Plasmadynamik (3)
- Plasmamedizin (3)
- Plasmarandschicht (3)
- Polyelektrolyt (3)
- Quantenoptik (3)
- Tokamak (3)
- Turbulenz (3)
- laser spectroscopy (3)
- mass separation (3)
- negative ions (3)
- oxygen (3)
- plasma diagnostics (3)
- polyanion (3)
- tokamak (3)
- 3D (2)
- Alfvén-Welle (2)
- Anion (2)
- Barrierenentladung (2)
- Cardiolipin (2)
- Clusterphysik (2)
- Computerphysik (2)
- Diffusion (2)
- Driftwelle (2)
- Dynamik (2)
- Emissionsspektroskopie (2)
- FT-IR-Spektroskopie (2)
- FTIR spectroscopy (2)
- Festkörper (2)
- Floquet (2)
- Flugzeitmassenspektrometrie (2)
- Fragmentation (2)
- Fullerene (2)
- Fusionsreaktor (2)
- Graphen (2)
- Heißes Plasma (2)
- Impurities (2)
- Infrarotspektroskopie (2)
- Instabilität (2)
- Kaltes Plasma (2)
- Kernstruktur (2)
- Laser (2)
- Leuchtstofflampe (2)
- Low Temperature Plasma (2)
- MR-ToF MS (2)
- MR-ToF device (2)
- Magnetfeld (2)
- Magnetic Confinement (2)
- Magnetische Rekonnexion (2)
- Magnetohydrodynamik (2)
- Magnetron (2)
- Monte-Carlo-Simulation (2)
- Multi-reflection time-of-flight mass spectrometry (2)
- Nuclear Physics (2)
- Optomechanik (2)
- Plasma physics (2)
- RNS (2)
- Rekonstruktion (2)
- Sekundärelektronen (2)
- Stereoskopie (2)
- Theoretische Physik (2)
- W7-AS (2)
- W7-X (2)
- atomic clusters (2)
- atomic force microscopy (2)
- cell mechanics (2)
- cold physical plasma (2)
- complex plasma (2)
- dusty plasmas (2)
- electrode (2)
- electron–hole plasma (2)
- erosion (2)
- gap voltage (2)
- guided streamer (2)
- inductively coupled plasma (2)
- ion mass spectrometry (2)
- ionosphere (2)
- laser photodetachment (2)
- laser-induced fluorescence (2)
- low temperature plasma (2)
- magnetic fields (2)
- mapping (2)
- memory effect (2)
- microwave interferometry (2)
- mode transition (2)
- numerical simulation (2)
- plasma chemistry (2)
- plasma medicine (2)
- polyelectrolyte multilayer (2)
- pre-ionization (2)
- reconstruction (2)
- solar EUV (2)
- stereoscopy (2)
- topologische Isolatoren (2)
- turbulence (2)
- 4D flow MRI (1)
- 52.27.Lw (1)
- 52.50.Dg (1)
- 52.65.-y (1)
- 52.75.Hn (1)
- 52.80.Hc (1)
- 7755384-6 (1)
- 89.75.Fb (1)
- ARPES (1)
- ASDEX (1)
- ASDEX Upgrade (1)
- Ab-initio-Rechnung (1)
- Abregung (1)
- Absorption Spectroscopy (1)
- Adsorption (1)
- Alfven (1)
- Alfvén Waves (1)
- Algorithm (1)
- Algorithmen (1)
- Algorithmus (1)
- Aluminium Cluster (1)
- Aluminium cluster (1)
- Aminogruppe (1)
- Anode (1)
- Antikoagulans (1)
- Antrieb (1)
- Argon metastables (1)
- Artificial nerual networks (1)
- Astrophysik (1)
- Atmospheric pressure plasma (1)
- Atmosphärendruckentladung (1)
- Atomemissionsspektroskopie (1)
- Atomspektrum (1)
- Auftrittsgröße (1)
- BAM (1)
- Barium (1)
- Bayes'sche Datenanalyse (1)
- Bayes-Verfahren (1)
- Bayesian Data Analysis (1)
- Beam (1)
- Biasing (1)
- Biomechanics (1)
- Biomolecules (1)
- Blei (1)
- Bogenentladung (1)
- Boltzmann equation (1)
- Bootstrap current (1)
- Bose-Einstein Kondensation (1)
- Bose-Einstein condensation (1)
- Bose-Einstein-Kondensation (1)
- Brennfleck (1)
- Brewster angle microscopy (1)
- Bürstenpolymere (1)
- CD Spektroskopie (1)
- Cadmium (1)
- Cavity Enhanced Absorption Spectroscopy (1)
- Cavity Ring-Down Spectroscopy (1)
- Cavity-Enhanced-Absorptionsspektroskopie (1)
- Cavity-Ring-Down-Spektroskopie (1)
- Cell biophysics (1)
- Cell cultures (1)
- Cell mechanics (1)
- Cell processes and subcellular processes (1)
- Cells (1)
- Cluster beam (1)
- Cluster charge (1)
- Cluster flow (1)
- Cluster formation (1)
- CoFeB (1)
- Coatings (1)
- Coil Optimization (1)
- Collisions (1)
- Colloidal Probe Technique (1)
- Complex plasma (1)
- Computersimulation (1)
- Connection length (1)
- Correlation Analysis (1)
- DBD (1)
- DIT (1)
- De-Excitation (1)
- Dense Plasmas (1)
- Density (1)
- Destabilisierung (1)
- Detachment (1)
- Diagnostik (1)
- Diamant (1)
- Dichte Plasmen (1)
- Dichtematrix (1)
- Dielectric Barrier Discharge (1)
- Dielektrische Entladung (1)
- Digital Ion Trap (1)
- Digital ion trap (1)
- Digitale Ionenfalle (1)
- Dirac-cone physics (1)
- Direct Force Measurement (1)
- Dispersion function (1)
- Dispersionsrelation (1)
- Dissipation (1)
- Domänen-Wachstum (1)
- Doppler cooling (1)
- Driftwellen (1)
- Duennschichten (1)
- Dust acoustic waves (1)
- Dusty Plasma (1)
- Dusty plasma (1)
- Dämpfung (1)
- Dünne Schicht (1)
- Dünne Schichten (1)
- Dünnes Plasma (1)
- ECRH (1)
- EEDF (1)
- EEVF (1)
- EPR (1)
- Edelgas (1)
- Effluent (1)
- Elastizität (1)
- Electric Propulsion (1)
- Elektrische Polarisation (1)
- Elektrode (1)
- Elektron (1)
- Elektronegative Plasmen / negative Ionen (1)
- Elektronenbad (1)
- Elektronenemission (1)
- Elektronenparamagnetische Resonanz (1)
- Emission (1)
- Emission Spectroscopy (1)
- Emitter (1)
- Empfindlichkeit (1)
- Energiereiches Teilchen (1)
- Entropie (1)
- Erosion (1)
- Escape factor (1)
- ExB-Drift (1)
- ExB-drift (1)
- Expansion (1)
- Exziton (1)
- FT-ICR-Spektroskopie (1)
- FTIR (1)
- FTIR-Spektrometrie (1)
- Far (1)
- Fast Particles (1)
- FeSe (1)
- Femtosecond lasers (1)
- Fernerkundung (1)
- Finite Systeme (1)
- Finite-element analysis (1)
- Fluid flows (1)
- Fluid-Modellierung (1)
- Fluorkohlenstoffhaltigen Plasmen (1)
- Fluorocarbon Plasmas (1)
- Flüssigkeiten (1)
- Fourier analysis (1)
- Fusion , Plasma , Plasmaphysik (1)
- Fusion plasma (1)
- Fusion plasmas (1)
- F‐actin (1)
- GPU computing (1)
- GaAs sputtering (1)
- Gas Cell (1)
- Gaselektronik (1)
- Gasphasenabscheidung (1)
- Gaszelle (1)
- Gaussian beam (1)
- Glass (1)
- Glimmentladung (1)
- Glimmentladungsspektroskopie (1)
- Graphene (1)
- Green-Funktion (1)
- Greenwald (1)
- Group (1)
- Guided Streamer (1)
- Gyro-kinetic Theory (1)
- Gyrokinetik (1)
- H-L back transition (1)
- Heat flux (1)
- Heat load (1)
- Heat-flux (1)
- Heparin (1)
- Heterostructures (1)
- Heterostrukturen (1)
- HiPIMS (1)
- High-Precision Mass Spectrometry (1)
- High-Temperature (1)
- Hoch Performanz (1)
- Hochfrequenzentladung (1)
- Hochfrequenzplasma / Plasmadynamik / Interferometrie / Photodetachment / Sauerstoff Plasma (1)
- Hot plasma (1)
- Hy (1)
- Hydrogen peroxide (1)
- Hydroperoxyl (1)
- IR-TDLAS (1)
- ISOLDE/CERN (1)
- ISOLTRAP (1)
- Informationstheorie (1)
- Infrarot (1)
- Infrarotabsorption (1)
- Innere Energie (1)
- Instrumentation for FEL (1)
- Instrumentation for radioactive beams (fragmentation devices, fragment and isotope, separators incl. ISOL, isobar separators, ion and atom traps, weak-beam diagnostics, radioactive-beam ion sources) (1)
- Ion Thruster (1)
- Ion Traps (1)
- Ion thrusters (1)
- Ion traps (1)
- Ionenbeschuss (1)
- Ionenfallen (1)
- Ionenstrahlfalle (1)
- Ionentriebwerk (1)
- Ionthruster (1)
- Isothermal Titration Calorimetry (1)
- Kalorimetrie (1)
- Kathode (1)
- Kerr microscopy (1)
- Kinetic Transport Theory (1)
- Kinetic simulation (1)
- Kinetische Gastheorie (1)
- Kinetische Theorie (1)
- Kinetische Transporttheorie (1)
- Kondo effect (1)
- Konformation (1)
- Kontaktmodell (1)
- Kontraktion (1)
- Kontrolle (1)
- Korrespondenzprinzip (1)
- Kraftmikroskopie (1)
- Künstliche Intelligenz (1)
- LE/LC phase transition (1)
- Laboratory experiment (1)
- Laboratory procedures (1)
- Laborexperiment (1)
- Ladungsdichtewelle (1)
- Ladungstransfer (1)
- Laminar flows (1)
- Langmuir Monolayers (1)
- Langmuir probe (1)
- Langmuir probe diagnostics (1)
- Langmuir-Blodgett and Schaefer techniques (1)
- Langmuir-Sonde (1)
- Laser spectroscopy (1)
- Laser-Cluster-Wechselwirkung (1)
- Laser-cluster interaction (1)
- Laser-induced fluoresence (LIF) (1)
- Laserheizung (1)
- Least-squares method (1)
- Lipid monolayers (1)
- Lipid-Monoschichten (1)
- Lipid-Oxidation (1)
- Low temperature plasma (1)
- Luftleuchten (1)
- L–H transition (1)
- MG-63 (1)
- MIR-Spektroskopie (1)
- Machine learning (1)
- Madden-Julian Oscillation (1)
- Magnetfelddiagnostik (1)
- Magnetic edge properties (1)
- Magnetic field diagnostics (1)
- Magnetic fields (1)
- Magnetic reconnection (1)
- Magnetische Rekonnektion (1)
- Magnetischer Einschluss (1)
- Magnetischer Sensor (1)
- Magnetismus (1)
- Magnetized (1)
- Magnetron sputtering (1)
- Marangoni flow (1)
- Mass Specrtometry (1)
- Mass spectrometers (1)
- Mass spectrometry (1)
- Master-Gleichung (1)
- Matrix (1)
- Mechanical properties (1)
- Mechanical stress (1)
- Mechanik (1)
- Mehrfach negativ geladene (1)
- Metall-Isolator-Phasenumwandlung (1)
- Microfluidic devices (1)
- Microfluidics (1)
- Microgravity (1)
- Microwave interferometry / Electron density / Laserphotodetachment (1)
- Mid-IR absorption spectroscopy (1)
- Mikrofluidik , Mechanik , Zelle , Holographie , Hologramm , Deformation , Biomedizin , Bluttransfusion , Cytometrie , Viskoelastizität (1)
- Mineral (1)
- Model Membranes (1)
- Modell (1)
- Modellbildung (1)
- Moden (1)
- Modendynamik (1)
- Modenübergang (1)
- Molecular Kinetics (1)
- Molekulardynamik (1)
- Molekülkinetik (1)
- Monoschicht (1)
- Multischicht (1)
- N incorporation (1)
- NBI (1)
- NEXT (1)
- Nachstellungsszenarien (1)
- Nachtluftleuchten (1)
- Nanocluster (1)
- Nanokompositschichten (1)
- Nanopartikel (1)
- Nanoplasmamodell (1)
- Negative ion (1)
- Neoclassical transport (1)
- Nerve cells (1)
- Neutral Beam Injection (1)
- Neutralisation (1)
- Neutralization (1)
- Neutrino (1)
- Neutronenbeugung (1)
- Neutronenstern (1)
- Nichtgleichgewicht (1)
- Nichtlineare Dynamik (1)
- Niederdruckplasma (1)
- Niedertemperatur-Plasma (1)
- Nuclear Structure (1)
- Nuclear fusion (1)
- Nukleosynthese (1)
- OLR-based MJO Index (1)
- OMI (1)
- Oberfläche (1)
- Oberflächenkräfte (1)
- Oberflächenladungen (1)
- Oberflächenmodifizierung (1)
- Oberflächenstöße (1)
- Operante Konditionierung (1)
- Optisches Messgerät (1)
- Oxidative stress (1)
- P3M (1)
- PDADMA (1)
- PEI,PDADMA,PSS,surface forces,atomic force microscopy, colloidal probe (1)
- PIC (1)
- PSS (1)
- PWV (1)
- Parallelstrom (1)
- Particle flux (1)
- Particle in Cell Simulation (1)
- Particle-in-Cell (1)
- Particle-in-cell (1)
- Particle-in-cell method (1)
- Paul-Falle (1)
- Penning Trap (1)
- Penning-Falle (1)
- Phase transitions (1)
- Phasenübergänge (1)
- Phospholipide (1)
- Phospholipids (1)
- Photoströme (1)
- Plasma , Plasmaphysik , Laser , Fluoreszenz , Interferometer , Wakefield , CERN , Kielfeld-Beschleuniger , Teilchenbeschleuniger , Laserinduzierte Fluoreszenz (1)
- Plasma , Plasmaphysik , Tokamak , Stellarator , Magnetohydrodynamik , Kinetische Theorie , Simulation , Alfvén-Welle , Energiereiches Teilchen (1)
- Plasma / Turbulenz (1)
- Plasma Chemistry (1)
- Plasma Instability (1)
- Plasma Modeling (1)
- Plasma Surface Interaction (1)
- Plasma diagnostics (1)
- Plasma diagnostics techniques and instrumentation (1)
- Plasma dynamics (1)
- Plasma medicine (1)
- Plasma surface interaction (1)
- Plasma-Flüssigkeits-Wechselwirkung (1)
- Plasma-Oberflächen-Wechselwirkung (1)
- Plasma-wall interaction (1)
- Plasmainstabilität (1)
- Plasmajet (1)
- Plasmanitrieren (1)
- Plasmaschwingung (1)
- Plasmasimulation (1)
- Plasmasonde (1)
- Plasmaspektroskopie (1)
- Plasmastrom (1)
- Plasmatheorie (1)
- Plasmatransport (1)
- Plasmawelle (1)
- Polarisation (1)
- Polaron (1)
- Polyanionen (1)
- Polyanions (1)
- Polydimethylsiloxan (1)
- Polyelektrolytbürste (1)
- Polymere (1)
- Polystyrolsulfonate (1)
- Potenzialhyperfläche (1)
- Power decay (1)
- Proteine (1)
- Präzisionsmassenmessung (1)
- Python (1)
- QCLAS (1)
- Quadrupole mass filter (1)
- Quantendot (1)
- Quantenkaskadenlaser (1)
- Quantenmechanik (1)
- Quantenphasenübergang (1)
- Quantenpunkt (1)
- Quantentheorie (1)
- Quantum Cascade Laser (1)
- RF Plasma (1)
- RF mass Spectrometry (1)
- ROS (1)
- ROS, cell and mitochondria mechanics (1)
- Radial axis shift (1)
- Radioactive Ion Beams (1)
- Radioaktivität (1)
- Radiofrequenz (1)
- Rasterkraftmikroskop (1)
- Rasterkraftmikroskopie (1)
- Reaktionsdynamik (1)
- Reinforcement learning (1)
- Relativistische Quantenmechanik (1)
- Relaxationskinetik (1)
- Renormalization (1)
- Robust (1)
- Rohstoffgewinnung (1)
- Rotational transform (1)
- Rydberg excitons (1)
- Röntgenbeugung (1)
- S/XB coefficient (1)
- Sauerstoff (1)
- Schadstoffabbau (1)
- Schaumflotation (1)
- Schlieren (1)
- Schnelles Teilchen (1)
- Schnittstelle (1)
- Schwerelosigkeit (1)
- Scrape-off layer width (1)
- Scraper (1)
- Secondary Electrons (1)
- Seebeck effect (1)
- Selbstorganisation (1)
- Self-absorption (1)
- Shape dynamics (1)
- Sheath transmission coefficient (1)
- Signal-to-noise ratio (1)
- Silber (1)
- Simulationsexperiment (1)
- Spectral imaging (1)
- Spectroscopy (1)
- Spin Trap (1)
- Spin Trapping (1)
- Spintronic devices (1)
- Spintronik (1)
- Sputterdeposition (1)
- Stark gekoppelte Systeme (1)
- Staub (1)
- Staubdichtewelle (1)
- Staubige Plasmen (1)
- Staubiges Plasma (1)
- Stickstoff (1)
- Stickstoff-Sauerstoff-Gemisch (1)
- Stickstoffgruppe (1)
- Stochstic Programming (1)
- Stoffwandlung (1)
- Stoß (1)
- Streutheorie (1)
- Strikeline (1)
- Sulfide (1)
- Supervised learning (1)
- Surface Collisions (1)
- Symmetrie (1)
- TDLAS (1)
- THz (1)
- TMCL (1)
- TOF (1)
- Temperatur (1)
- Terahertz radiation (1)
- Terahertz spectroscopy (1)
- Theoretical Physics (1)
- Thermografie (1)
- Thin films (1)
- Thrombozytopenie (1)
- Ti-Cu-N coating (1)
- Time-of-flight mass spectrometry (1)
- Titan Tholins (1)
- Titan-Tholine (1)
- Tomographie (1)
- Topologischer Isolator (1)
- Tracer particles (1)
- Tracerpartikel (1)
- Transmission electron microscopy (1)
- Transporttheorie (1)
- Turbulente Strömung (1)
- UV-VIS-Spektroskopie (1)
- VUV-Strahlung (1)
- Velocity distribution (1)
- Verdampfung (1)
- Verschränkung (1)
- Verunreinigungstransport (1)
- Vielteilchensystem (1)
- Vielteilchentheorie (1)
- Viscoelastic properties (1)
- Vorionisation (1)
- WSS (1)
- Wand-Abregung-Wahrscheinlichkeit (1)
- Waves (1)
- Wellen (1)
- Wellenmagnetfeld (1)
- Wellenwechselwirkung (1)
- Wendelstein (1)
- Wendelstein 7-x (1)
- Whistlerwelle (1)
- Wolfram (1)
- X-ray diffraction (1)
- X-ray photoelectron spectroscopy (1)
- Zeeman and Stark effects (1)
- Zeeman- und Stark-Effekte (1)
- Zelle (1)
- Zellmechanik (1)
- Zitterbewegung (1)
- absorption spectroscopy (1)
- actin cytoskeleton (1)
- actin quantification (1)
- airglow (1)
- alumina (1)
- amino polymer (1)
- anomal transport (1)
- anomaler Transport (1)
- anti-adhesive surface (1)
- antimatter plasma (1)
- aortic arch (1)
- appearance size (1)
- atherosclerosis (1)
- atmosphere (1)
- atmospheric pressure discharge (1)
- atmospheric pressure plasma (1)
- atomic level scheme (1)
- atomic masses of cesium isotopes (1)
- atomic spectra (1)
- barrier corona (BC) (1)
- bipolar pulse (1)
- borosilicate (1)
- calcium ion signaling (1)
- cathodes (1)
- cavity QED (1)
- cavity ring-down (1)
- cell adhesion (1)
- cell membrane (1)
- cell spreading (1)
- cell-material interaction (1)
- cell‐surface contacts (1)
- charge measurement (1)
- charge-density-wave (1)
- climate (1)
- cluster (1)
- cold atmospheric pressure plasmajet (1)
- combination therapy (1)
- complex plasmas (1)
- computer vision (1)
- consistent (1)
- contact model (1)
- control (1)
- copper nitride (1)
- correlation analysis (1)
- coupled phonon-plasmon modes (1)
- crystal structure (1)
- cylindrical wave (1)
- data-mining (1)
- density limit (1)
- diagnostics (1)
- dice lattice (1)
- dielectric barrier discharge (DBD) (1)
- dielectric response (1)
- dielektrisch behinderte Entladung (1)
- diffusion within multilayers (1)
- dipole magnetic field (1)
- discharge evolution (1)
- discharge mode transition (1)
- disruption (1)
- divertor (1)
- domain growth (1)
- drift waves (1)
- dust (1)
- dust charge (1)
- dust-density waves (1)
- electric field (1)
- electric propulsion (1)
- electrochemistry (1)
- electron bath (1)
- electron cyclotron emission (1)
- electron emission (1)
- electron energy loss spectroscopy (1)
- electronegativity (1)
- electronic structure (1)
- electron–positron plasma (1)
- ellipsometry (1)
- energetic ion (1)
- energy-resolved ion mass spectrometry (1)
- entanglement (1)
- entropy (1)
- evaporation (1)
- fast optical and electrical diagnostics (1)
- fdtd (1)
- finite difference in time domain (1)
- finite systems (1)
- flow dynamics (1)
- fluid modelling (1)
- fluid simulation (1)
- fluorescence (1)
- fluorescent lamp (1)
- fluorescent lamps (1)
- food quality (1)
- forcing (1)
- fractals (1)
- froth flotation (1)
- ftir spectroscopy (1)
- full-wave (1)
- fusion plasma (1)
- gas cell (1)
- gepulster Betrieb (1)
- glow-like discharge (1)
- glow-to-arc transition (1)
- gyrokinetic (1)
- gyrokinetics (1)
- gyrokinetisch (1)
- heavy actinides (1)
- helicon, fluorescence, accelerator (1)
- helium barrier discharge (1)
- helium–oxygen barrier discharge (1)
- high performance (1)
- high power impulse magnetron sputtering (1)
- high spatial resolution (1)
- hollow cathode discharge (1)
- hot spot (1)
- human osteoblasts (1)
- hydrogen peroxide (1)
- in situ (1)
- in-situ Diagnostik (1)
- inflammatory/immunological response (1)
- infrared spectroscopy (1)
- inhomogeneous plasma (1)
- inhomogenes plasma (1)
- instabilities (1)
- interchange (1)
- internal energy (1)
- intramuscularly implantation (1)
- intraseasonal variation (1)
- ion accelerator (1)
- ion composition (1)
- ion drag (1)
- ion traps (1)
- ion-beam trap (1)
- ionenwind (1)
- ionosphere modeling (1)
- ipf-fd3d (1)
- iron based superconductors (1)
- isotherms (1)
- kinetic modelling (1)
- konsistent (1)
- laser atomic absorption (1)
- laser heating (1)
- laser photodesorption (1)
- layer-by-layer (1)
- leafy greens (1)
- lebensdauerabhängige Auftrittsgrößen (1)
- lifetime-depentend appearance size (1)
- lipid domain growth (1)
- lipid monolayer (1)
- lipid oxidation (1)
- low-temperature plasma (1)
- low-temperature plasma polymerization (1)
- low‐temperature plasma (1)
- magic number (1)
- magnesia (1)
- magnetic characterization methods (1)
- magnetic field (1)
- magnetic materials (1)
- magnetic microscopy (1)
- magneto-hydrodynamic equilibrium (1)
- magneto-optical effects (1)
- magneto-optics (1)
- magnetron sputtering discharge (1)
- mass spectrometer (1)
- mass spectrometry (1)
- mathematical modeling (1)
- medical gas plasma technology (1)
- melamine-formaldehyde (1)
- metal-insulator transition (1)
- microcontact printing (1)
- microdischarge (1)
- microfluidics, cell mechanics, cells, holography, hologram, deformation, biomedicine, transfusion medicine, cytometry, viscoelasticity (1)
- microgravity research (1)
- microinstabilities (1)
- microinstabilitäten (1)
- microwave-driven discharge (1)
- mimic scenario (1)
- mixed-valence correlations (1)
- mode dynamics (1)
- modeling (1)
- modern experimental methods (1)
- molecular ion formation (1)
- monolayer (1)
- mouse (1)
- multi-reflection time-of-flight mass spectrometry (1)
- multilayer composition (1)
- multilayers (1)
- multiview geometry (1)
- mutlinucleon transfer (1)
- nanoparticles (1)
- nanosecond-pulsed streamer (1)
- nanowire (1)
- negative Ionen (1)
- nematicity (1)
- neoclassic (1)
- neoklassisch (1)
- networks (1)
- neural (1)
- neuron-rich calcium isotopes (1)
- neutral recycling (1)
- neutron reflectometry (1)
- neutron-rich nuclei (1)
- nicht-Hermitizität (1)
- nichtlinear (1)
- nightglow (1)
- nitrogen metastables (1)
- nitrogen-oxygen gas mixtures (1)
- non-Hermitian (1)
- non-equilibrium (1)
- non-thermal processing (1)
- nonlinear dynamics (1)
- numerische simulation (1)
- offene Quantensysteme (1)
- oncology (1)
- open quantum systems (1)
- optical diagnostics (1)
- optical emission and absorption spectroscopy (1)
- optical emission spectroscopy (1)
- optomechanics (1)
- osteoblasts (1)
- oxidation processes (1)
- pair plasma (1)
- parallel current (1)
- paramagnetic particles (1)
- partial discharge (PD) (1)
- partial mutual information (1)
- particle (1)
- particle tracking (1)
- particle transport (1)
- particle-in-cell (1)
- patterned discharge (1)
- penning trap mass spectrometer ISOLTRAP (1)
- permutation (1)
- phase resolved surface charge measurement (1)
- phase separation (1)
- phonon localization (1)
- phonon propagation (1)
- photocurrent (1)
- photodetachment spectroscopy (1)
- phototdissociation (1)
- pinch (1)
- plaque characteristics (1)
- plasma applications (1)
- plasma confinement (1)
- plasma current (1)
- plasma devices (1)
- plasma diagnostic (1)
- plasma in liquids (1)
- plasma instabilities (1)
- plasma jet (1)
- plasma material processing (1)
- plasma modeling (1)
- plasma physics (1)
- plasma science and technology (1)
- plasma sheaths (1)
- plasma simulation (1)
- plasma theory (1)
- plasma-fluorocarbon-polymer (1)
- plasma-liquid-interaction (1)
- platelet biomechanics (1)
- platelet cytoskeleton (1)
- plume (1)
- pollution control (1)
- polyelectrolyte (1)
- polyelectrolytes (1)
- positive Säule (1)
- positive column (1)
- positively biased anode (1)
- positron beam (1)
- precision mass measurements (1)
- pulse length dependence (1)
- pulsed laser deposition (1)
- pulsed operation (1)
- pulsed power (1)
- pump-probe spectroscopy (1)
- quantum cascade laser (1)
- quantum corrections (1)
- quantum phase transition (1)
- quasi-two-dimensional systems (1)
- r-Prozess (1)
- radiation detection (1)
- radioactive nuclei (1)
- reactive mode (1)
- reactive oxygen and nitrogen species (1)
- reactive oxygen species (1)
- ready-to-eat produce (1)
- real‐time deformability cytometry (1)
- remote (1)
- resistive ballooning (1)
- resonance ionization (1)
- retrieval (1)
- roadmap (1)
- rule changes (1)
- scanning ion conductance microscopy (1)
- scattering processes (1)
- schnelle optische und elektrische Diagnostik (1)
- scrape-off layer (1)
- secondary electron emission (1)
- secondary electron emission coefficient (1)
- secondary electrons (1)
- seed electrons (1)
- self-assembly (1)
- semi-empirical (1)
- sensitivity (1)
- separatrix (1)
- shear flow (1)
- short-lived nuclides (1)
- similarity laws (1)
- similarity scaling (1)
- simulation (1)
- simulations (1)
- skyrmions (1)
- solar variability (1)
- solenoid separator (1)
- solid-state physics (1)
- space charge (1)
- species conversion (1)
- spin-polarized current (1)
- statistical analysis (1)
- strain fields (1)
- strong correlations (1)
- superconductivity (1)
- superoxide anion (1)
- superposed epoch analysis (1)
- supported lipid bilayers (1)
- surface charge sensing (1)
- surface charges (1)
- surface double layer (1)
- surface electrons (1)
- surface forces (1)
- surface physics (1)
- symmetry (1)
- temperature (1)
- terahertz ellipsometry (1)
- terahertz emission spectroscopy (1)
- terahertz spintronics (1)
- terahertz time‐domain spectroscopy (1)
- terahertz transmission spectroscopy (1)
- theoretical description and modelling (1)
- thermionische Emission (1)
- thermography (1)
- thermosphere (1)
- thin film deposition (1)
- thin films (1)
- thrusters (1)
- time-correlated single photon counting (TC-SPC) (1)
- time-resolved optical emission spectroscopy (1)
- titanium (Ti) alloys (1)
- titanium surface modification (1)
- topological insulator (1)
- topological insulators (1)
- transient spark (1)
- transport coefficients (1)
- tumor immunology (1)
- tunable diode laser absorption spectroscopy (1)
- tungsten (1)
- two-photon absorption laser-induced fluorescence (1)
- ultrafast spincaloritronics (1)
- ultrafast spintronics (1)
- valleytronics (1)
- vision (1)
- voltage stabilization (1)
- wave interaction (1)
- wave magnetic field (1)
- weather forecasting (1)
- wettability (1)
- wetted area (1)
- whistler wave (1)
- zeta potential (1)
- zylindrische Welle (1)
- Überwachtes Lernen (1)
Institute
- Institut für Physik (244) (remove)
Publisher
- IOP Publishing (63)
- MDPI (13)
- Copernicus (7)
- AIP Publishing (5)
- Frontiers Media S.A. (4)
- American Physical Society (APS) (3)
- Springer Nature (3)
- Cambridge University Press (2)
- European Geosciences Union (2)
- John Wiley & Sons, Ltd (2)
In this thesis we have revisited the formation of the excitonic insulator (EI), which realizes an exciton condensate. In contrast to optically created exciton condensates, the EI forms in thermal equilibrium and is solely driven by the Coulomb attraction between electrons and holes. The EI phase is anticipated to occur near the semimetal-semiconductor (SM-SC) transition at low temperatures. Depending from which side the EI is approached, it forms due to a BCS-type condensation of electron-hole pairs or a Bose-Einstein condensation (BEC) of excitons. The extended Falicov-Kimball model (EFKM) is the minimal model the EI can be described with. This model describes spinless fermions in two dispersive bands (f band and c band), that interact via a local Coulomb repulsion. The EFKM is also used to describe electronic ferroelectricity (EFE). Both phases, the EI and EFE-type ordering, are characterized by a spontaneous f-c hybridization in the EFKM. We have presented the EI phase, the EFE phase, and the orderings they compete with. Moreover, we have determined the ground-state phase diagram of the EFKM. We have focused particularly on the anticipated BCS-BEC crossover within the EI and have analyzed the formation scenarios. The exciton spectrum and the exciton density in the normal phase close to the critical temperature give information about relevant particles and therefore the nature of the transition. We have demonstrated that the whole EI is surrounded by a halo", that is, a phase composed of electrons, holes and excitons. However, on the SM side, only excitons with a finite momentum exist. These excitons appear only in a small number and barely influence the SM-EI transition. This phase transition is driven by critical electron-hole fluctuations, generated by electrons and holes at the Fermi surface. On the SC side, excitons with arbitrary momenta exist. Most notably, we have found the number of zero-momentum excitons to diverge at the SC-EI transition, signaling the BEC of these particles. Within the EI phase, there is a smooth crossover from the BCS regime to the BEC regime. One of the promising candidates to observe the EI experimentally, is the transition-metal dichalcogenide 1T-TiSe2. Strong evidences were found favoring an EI scenario of the charge-density-wave (CDW) formation in this material. However, some aspects point to a lattice instability to drive the CDW transition. We have addressed this issue by analyzing the recently discovered chiral property of the CDW in 1T-TiSe2. We have found that the EI scenario is insufficient to explain a stable, long range chiral charge ordering. Lattice degrees of freedom must be taken into account. In particular, nonlinear electron-phonon coupling and phonon-phonon interaction are crucial. By estimating appropriate model parameters for 1T-TiSe2, we have suggested a combination of excitonic and lattice instability to drive the CDW transition in this material. Experiments in 1T-TiSe2 and other materials suggest that the coupling to the lattice is non-negligible. We have extended therefore the model by an explicit exciton-phonon interaction, and have analyzed crucial effects of this interaction. While the single-particle spectrum is not modified qualitatively, the electron-hole pair spectrum changes significantly. The inclusion of the phonons lead to a massive collective mode in the ordered ground state in contrast to the case for vanishing exciton-phonon coupling, where the mode is acoustic. We have suggested that a gapless collective mode leads to off-diagonal long range order. This questions that the ground state for finite exciton-phonon coupling represents a condensate.
The region surrounding the excitonic insulator phase is a three-component plasma composed of electrons, holes, and excitons. Due to the extended nature of the excitons, their presence influences the surrounding electrons and holes. We analyze this correlation. To this end, we calculate the density of bound electrons, the density of electrons in the correlated state, the momentum-resolved exciton density, and the momentum-resolved density of electron-hole pairs that are correlated but unbound. We find qualitative differences in the electron-hole correlations between the weak-coupling and the strong-coupling regime.
In the present thesis, a systematic study of beam driven Alfvén eigenmodes in high-density and low-temperature plasmas of the W7-AS stellarator is performed. The device went out of operation in 2002 and the study is based on stored experimental data. Alfvén instabilities can roughly be divided into ideal MHD Alfvén eigenmodes and those existing due to kinetic effects. The spectrum of ideal MHD Alfvén waves in toroidal fusion devices consists of a continuum of stable waves that are strongly localized. Weakly damped, discrete eigenmodes can exist in gaps of the continuous spectrum which are formed by plasma inhomogeneities and the coupling of Alfvén continua. This allows an identification of ideal MHD Alfvén eigenmodes in terms of their frequency and mode numbers. Kinetic effects can modify this spectrum and cause additional types of eigenmodes, the kinetic Alfvén eigenmodes (KAE) and energetic particle modes (EPM). The goal of this thesis is twofold: (I) identification and description of fast particle driven Alfvén instabilities in W7-AS, and (II) study of energetic particle losses induced by Alfvén instabilities. The reconstruction of the ideal MHD plasma equilibrium for each discharge with sufficient accuracy is the very foundation of all subsequent steps. This is achieved, based on measured plasma parameter profiles that are further refined by validating them to the measurements of other, independent plasma diagnostics. The applied scheme is inspired by an approach of Integrated Data Analysis (IDA) to combine different diagnostic data and provide combined uncertainties. After mode number analysis and eigenmode identification, the theoretically expected, linear growth rate of the instability is calculated where possible, and the various contributions of the fast particle drive to the instability of the mode are identified. Alfvénic activity recorded by the Mirnov diagnostic is analyzed, which consists of a set of spatially distributed coils that measure magnetic fluctuations. On W7-AS, the probes are arranged in three poloidal arrays at different toroidal positions. The spacing between the probes is non-equidistant. In addition, the signals of one probe array are digitized with a different sample rate. These characteristics prohibit the straight-forward use of standard tools available for harmonic analysis. Instead, a new tool has been developed and thoroughly tested. It is a multi-dimensional extension of the Lomb periodogram, able to provide reliable time-resolved frequency and mode number spectra in the case of uneven datapoint spacing. Numerical studies of this periodogram show a good performance with respect to mode number resolution given the low number of available probes, and robustness against perturbations of the signal. Only two of the probe arrays can be used for the analysis of eigenmodes with frequencies >70 kHz, such that for high-frequency phenomena insufficient information about the mode numbers is available. A total of 133 different Alfvén eigenmodes is studied in discharges from different experimental campaigns. A restriction to discharges from various high-beta campaigns with neutral beam heating is required to allow for a realistic reconstruction of plasma equilibrium and velocity distribution functions of energetic particles. The discharges are characterized by high density, ne = 5 x 1019 m-3 to 2.5 x 1020 m-3 at relatively low temperatures of Te = Ti = 150 ... 600 eV. Alfvén eigenmodes often appear transiently in the startup phase of these discharges, where density and heating power are being ramped up. Occasionally, Alfvén eigenmodes are seen in the stationary, high-beta phase in the presence of considerable neutral beam heating. Most of the Alfvén eigenmodes are successfully classified as ideal MHD eigenmodes. 19 global, 47 toroidicity-induced and 8 ellipticity-induced Alfvén eigenmodes (GAEs, TAEs, and EAEs, respectively) are unambiguously identified by their mode numbers and frequencies. Excellent agreement between experimentally observed mode number spectra and theoretically calculated eigenmode structure is shown for a TAE example. Additional 13 events are found to have frequencies inside the EAE gap and could possibly be EAEs. Evidence for high-frequency Alfvén eigenmodes (mirror- and helicity-induced Alfvén eigenmodes) is seen, but can not be proven rigorously due to uncertain mode numbers and the complexity of the Alfvén continuum. The remaining 41 Alfvén eigenmodes can not be classified to be one of the above cases. Reasons are either high frequencies, mode numbers obscured by far-field effects, or mode numbers that could not be related to ideal MHD Alfvén eigenmodes. A selection of these shows indications of strong non-linear wave-particle interactions and are assumed to be EPMs. Kinetic Alfvén eigenmodes are not expected to exist in the experimental conditions that were studied. The radially resolved velocity distribution function is used to describe the parameter regimes in which the modes are observed in terms of the dimensionless parameters vb/vA (beam velocity normalized to the Alfvén velocity) and ßfast/ßth, where beta is the ratio of plasma pressure to magnetic pressure. The first parameter describes through which of the possible resonance velocities particles can interact with the eigenmode. A peculiarity of the fast particle dynamics in fusion devices is that they can resonantly interact with Alfvén eigenmodes through sideband resonances even if v < vA. The second parameter describes the energy content of the destabilizing fast particle population compared to the potentially stabilizing thermal plasma component. These parameters contain relevant information about the instability of an eigenmode and such diagrams are given for all observed modes. In addition to that, the expected linear growth rate of gap modes is calculated based on a theoretical model that extends the ideal MHD by a perturbative, drift-kinetic description of the energy exchange between waves and circulating particles, neglecting the effects of trapped particles. For the discharges under consideration the thermal electron speed is comparable to vA and the electrons provide a significant Landau damping contribution. Due to strong density gradients near the plasma boundary in most of the discharges, the thermal ions can provide a small drive via the spatial inhomogeneity which does not overcome the electron damping, however. The drive by spatial inhomogeneity of thermal ions requires a certain propagation direction of the mode and is equally stabilizing for opposite mode numbers. The fast particles also contribute to the growth rate via spatial inhomogeneity, velocity gradients and velocity anisotropy terms are negligible in W7-AS. Most of the observed GAE or EAE modes have negative mode numbers, which correspond to a propagation direction for which the spatial inhomogeneity of thermal and beam ions is predicted to be stabilizing. A fast particle drive of these modes is not confirmed, whereas the TAEs are found to be strongly destabilized by neutral beam injection. The distribution of plasma parameters for discharges showing TAEs in terms of the dimensionless stability parameters suggests an instability threshold that is qualitatively confirmed by an exploration of the parameter space with the theoretical model. Wave-induced, resonant losses of energetic ions scale linearly with the wave amplitude. To identify them, correlations between ion loss probe signals and wave amplitudes are searched, where correlation times in the order of the slowing-down time of energetic particles are expected. Significant correlations can be established only exceptionally for 3 of the identified ideal MHD Alfvén eigenmodes. Those Alfvén eigenmodes, however, which are assumed to be EPMs frequently show severe losses of energetic ions that are visible in the time traces of the plasma energy as well.
The collisionless tearing mode is investigated by means of the delta-f PIC code EUTERPE solving the gyrokinetic equation. In this thesis the first simulations of electromagnetic non-ideal MHD modes in a slab geometry with EUTERPE are presented. Linear simulations are carried out in the cases of vanishing and finite temperature gradients. Both cases are benchmarked using a shooting method showing that EUTERPE simulates the linearly unstable tearing mode to a very high accuracy. In the case of finite diamagnetic effects and values of the linear stability parameter Delta of order unity analytic predictions of the linear dispersion relation are compared with simulation results. The comparison validates the analytic results in this parameter range. Nonlinear single-mode simulations are performed in the small- to medium-Delta range measuring the dependency of the saturated island half width on the equilibrium current width. The results are compared with an analytic prediction obtained with a kinetic electromagnetic model. In this thesis the first simulation results in the regime of fast nonlinear reconnection~(medium- to high-Delta range) are presented using the standard gyrokinetic equation. In this regime a nonlinear critical threshold has been found dividing the saturated mode from the super-exponential phase for medium-Delta values. This critical threshold has been proven to occur in two slab equilibria frequently used for reconnection scenarios. Either changing the width of the equilibrium current or the wave number of the most unstable mode makes the threshold apparent. Extensive parameter studies including the variation of the domain extensions as well as the equilibrium current width are dedicated to a comprehensive overview of the critical threshold in a wide range of parameters. Additionally, a second critical threshold for high-Delta equilibria has been observed. A detailed comparison between a compressible gyrofluid code and EUTERPE is carried out. The two models are compared with each other in the linear regime by measuring growth rates over wave numbers of the most unstable mode for two setups of parameters. Analytical scaling predictions of the dispersion relation relevant to the low-Delta regime are discussed. Employing nonlinear simulations of both codes the saturated island half width and oscillation frequency of the magnetic islands are compared in the small-Delta range. Both models agree very well in the limit of marginal instability and differ slightly with decreasing wave vector. Recently, the full polarisation response in the quasi-neutrality equation was implemented in EUTERPE using the Padé approximation of the full gyrokinetic polarisation term. Linear simulation results including finite ratios of ion to electron temperature are benchmarked with the dispersion relation obtained from a hybrid model. Finite temperature effects influence the saturated island width slightly with increasing ion to electron temperature ratio which has been verified by both models.
Optomechanical (om) systems are characterized by their nonlinear light-matter interaction. This is responsible for unique dynamic properties and allows the detection of a variety of classical and quantum mechanical phenomena on a microscopic as well as on a macroscopic scale. In this work we have studied the dynamic behavior of two laser-driven om systems, the single om cell ("cavity optomechanics / membrane-in-the-middle setup") and a two-dimensional hexagonal array of these cells ("om graphene"). The first case was motivated by the possibility to detect the transition from quantum mechanics to classical mechanics directly on the basis of the dynamic behavior. For this we focus on multistability effects of the optical and mechanical degrees of freedom, that are modeled by harmonic oscillators. Our description is based on the quantum optical master equation, which takes into account the environmental interaction assuming a vanishing temperature. As a consequence of decoherence, the dynamics occur near the semiclassical limit, i.e. it is characterized by quantum fluctuations. The quantum-to-classical transition is realized formally by rescaling the equations of motion. In the classical limit, quantum fluctuations disappear and the mean field equations were evaluated by analytical and numerical methods. We found that classical multistability is characterized by stationary signatures on the route to chaos, as well as by the coexistence of single-periodic orbits for the mechanical degree of freedom. The latter point was extensively evaluated by means of a self-consistent approach. For the dynamics in the quantum regime quantum fluctuations cannot be neglected. For this purpose, the master equation was solved by means of a numerical implementation of the Quantum State Diffusion (QSD) method. Based on Wigner and autocorrelation functions, we were able to show that quantum multistability is a dynamic effect: chaotic dynamics is suppressed and there is a time-dependent distribution of the phase space volume on classical simple-periodic orbits. The results can be interpreted within a semiclassical picture, which makes use of the single QSD quantum trajectory. Accordingly, the quantum-classical transition is explained as a time-scale effect, which is determined by tunneling probabilities in an effective mean-field potential. The subject of the second part of the work is the transport of low-energy Dirac quasiparticles in om graphene, propagating as light and sound waves. For this purpose, we investigated the scattering of a plane light wave by laser-induced photon-phonon coupling planar and circular barriers. The starting point is the om Dirac equation, which results from the continuum approximation of the Hamiltonian description of the two-dimensional array near the semiclassical limit. This work was motivated by the rich and interesting relativistic transport and tunneling phenomena found for electrons in graphene, which now appear in a new way. The reason is the presence of the new spin degree of freedom, which distinguishes the optical and mechanical excitations. In this spin space, the om interaction can be understood as a potential, which in our analysis consists of a time-independent and a time-dependent sinusoidal part. For the first case of a static barrier, the transport is elastic and is characterized by stationary scattering signatures. After solving the scattering problem via continuity conditions we were able to identify different scattering regimes depending on scattering parameters. In addition to relativistic phenomena such as Klein tunneling, simple parameter variation allows to use the barrier as a resonant light-sound interconverter and angle-dependent emitter. For the oscillating barrier, the transport is inelastic and is characterized by dynamic scattering signatures. To solve the time-periodic scattering problem, we have applied the Floquet theory for an effective two-level system. As a result of the barrier oscillation, photons and phonons can get and give away energy portions in the form of integer multiples of the oscillation frequency. The interference of short (classical) and long-wave (quantum) components leads to mixing of the scattering regimes. This allows to use the barrier as a time-periodic light-sound interconverter with interesting radiation characteristics. In addition, we have argued that the oscillating barrier provides the necessary energetic conditions for detecting zitterbewegung.
The stratospheric aerosol layer plays an important role in the radiative balance of Earth primarily through scattering of solar radiation. The magnitude of this effect depends critically on the size distribution of the aerosol. The aerosol layer is in large part fed by volcanic eruptions strong enough to inject gaseous sulfur species into the stratosphere. The evolution of the stratospheric aerosol size after volcanic eruptions is currently one of the biggest uncertainties in stratospheric aerosol science. We retrieved aerosol particle size information from satellite solar occultation measurements from the Stratospheric Aerosol and Gas Experiment III mounted on the International Space Station (SAGE III/ISS) using a robust spectral method. We show that, surprisingly, some volcanic eruptions can lead to a decrease in average aerosol size, like the 2018 Ambae and the 2021 La Soufrière eruptions. In 2019 an intriguing contrast is observed, where the Raikoke eruption (48∘ N, 153∘ E) in 2019 led to the more expected stratospheric aerosol size increase, while the Ulawun eruptions (5∘ S, 151∘ E), which followed shortly after, again resulted in a reduction in the values of the median radius and absolute distribution width in the lowermost stratosphere. In addition, the Raikoke and Ulawun eruptions were simulated with the aerosol climate model MAECHAM5-HAM. In these model runs, the evolution of the extinction coefficient as well as of the effective radius could be reproduced well for the first 3 months of volcanic activity. However, the long lifetime of the very small aerosol sizes of many months observed in the satellite retrieval data could not be reproduced.
This thesis describes the implementation and first on-line application of a multi-reflection time-of-flight (MR-ToF) mass analyzer for high-resolution mass separation at the ISOLTRAP mass spectrometer at ISOLDE/CERN. On the one hand, the major objective was to improve ISOLTRAPs mass-measurement capabilities with respect to the ratio of delivered contaminating ions to ions of interest. On the other hand, the time necessary to purify wanted from unwanted species should be reduced as much as possible to enable access to even more exotic nuclei. The device has been set up, optimized and tested at the University of Greifswald before its move to ISOLTRAP. The achieved performance comprises mass resolving powers of up to 200000 reached at observation times of 30ms and a contamination suppression of about four orders of magnitude by use of a Bradbury-Nielsen gate. With the characteristics, it outperforms clearly the so far state-of-the-art purification method of a gas-filled Penning trap. To improve the utilization of the MR-ToF mass analyzer, the in-trap lift method has been developed. It simplifies the application and optimization of the device, which is a crucial time factor in an on-line experiment. The device was the first of its kind successfully applied to radioactive ion beams for a mass analysis, for a mass separation (in combination with the Bradbury-Nielsen gate) as a preparatory step for a subsequent Penning-trap mass measurement and as a high-precision mass spectrometer of its own. The later was recently used for the first mass measurement of the neutron-rich calcium isotopes 53Ca and 54Ca. The so-far achieved mass-resolving power of 200000 belongs to the highest reported for time-of-flight mass analyzers at all. The first successful application of the MR-ToF system as the only mass separator at ISOLTRAP resulted in the mass measurement of 82Zn. The new mass value has been compared to mass extrapolations of the most recent Hartree-Fock-Bogoliubov (HFB) mass models, HFB-19 to HFB-21, of the BRUSLIB collaboration. The mass of the nuclide is of high interest for the compositions and depth profile of the outer crust of neutron stars. In the classical model of the outer crust of a cold, non-accrediting and non-rotating neutron star, the sequence of nuclides found within this parts is determined mainly by the binding energy of exotic nuclides. The crustal compositions determined with the three HFB mass models differed with respect to the appearance of a layer of 82Zn, originating from different mass extrapolations of this mass. With the new experimental data, the extrapolations could be evaluated. It was found that the HFB-21 mass value differs less from the experimental data than the ones from HFB-19 and 20. Therefore, in the classical model, 82Zn does not appear anymore in the outer crust. Due to its high resolution and very fast measurement time, the MR-ToF mass analyzer will be an important instruments for future activities at ISOLTRAP, at the ISOLDE facility in general, and at other radioactive ion-beam facilities.
Abstract
The presented experimental system is a barrier discharge system with plane parallel electrodes. The lateral surface charge distribution being deposited on the dielectric layer during each breakdown is observed optically using the well known electro-optic effect (Pockels effect). The temporal resolution of the surface charge measurement has been increased to 200 ns, and so for the first time it is possible to resolve the charge transfer to the dielectric surface in a single breakdown. In the present measurements, a patterned glow-like barrier discharge is investigated. It is found that the charge reversal in a single discharge spot (microdischarge) starts in the centre and then grows outwards. These experimental findings verify previously unconfirmed predictions from earlier numerical calculations and thereby contribute to a better understanding of the interaction between the plasma and the electrical charge on the electrodes.
Abstract
The surface charge distribution deposited by the effluent of a dielectric barrier discharge driven atmospheric pressure plasma jet on a dielectric surface has been studied. For the first time, the deposition of charge was observed phase resolved. It takes place in either one or two events in each half cycle of the driving voltage. The charge transfer could also be detected in the electrode current of the jet. The periodic change of surface charge polarity has been found to correspond well with the appearance of ionized channels left behind by guided streamers (bullets) that have been identified in similar experimental situations. The distribution of negative surface charge turned out to be significantly broader than for positive charge. With increasing distance of the jet nozzle from the target surface, the charge transfer decreases until finally the effluent loses contact and the charge transfer stops.
Behavior of a porous particle in a radiofrequency plasma under pulsed argon ion beam bombardment
(2010)
The behavior of a single porous particle with a diameter of 250 μm levitating in a radiofrequency (RF) plasma under pulsed argon ion beam bombardment was investigated. The motion of the particle under the action of the ion beam was observed to be an oscillatory motion. The Fourier-analyzed motion is dominated by the excitation frequency of the pulsed ion beam and odd higher harmonics, which peak near the resonance frequency. The appearance of even harmonics is explained by a variation of the particles's charge depending on its position in the plasma sheath. The Fourier analysis also allows a discussion of neutral and ion forces. The particle's charge was derived and compared with theoretical estimates based on the orbital motion-limited (OML) model using also a numerical simulation of the RF discharge. The derived particle's charge is about 7–15 times larger than predicted by the theoretical models. This difference is attributed to the porous structure of the particle.
This thesis describes mass measurements at ISOLTRAP/ISOLDE/CERN in the region of the neutron-rich calcium isotopes. For the less exotic and more abundantly produced isotopes 51Ca and 52Ca the Penning trap based ToF-ICR technique could be used to validate the available mass data and to improve their precision. For the isotopes 53Ca and 54Ca, a Multi-Reflection Time-of-Flight Mass Spectrometer (MR-ToF MS) was used to determine the mass of these exotic isotopes for the first time experimentally. This also represents the first time an MR-ToF MS was applied to derive the masses of previously unknown radioactive ions from the high precision time-of-flight data that can be gathered with the device. The mass data was then used to benchmark the strength of the N=32 neutron subshell closure and at the same time to compare to state-of-the-art shell-model calculations.
Furthermore, the capability of the MR-ToF device to deliver isobarically pure beams to a subsequent experiment was developed further and studied in detail. The new technique is based on the in-trap lift, which is normally used to in- and eject ions into and from the device. With this new selective ejection technique after separation of the ion ensemble in the MR-ToF trap, no external components are required.
Additionally, a new stabilization system for voltages supplies, based on a PI-algorithm, was developed and thoroughly tested. The stabilized voltage supply was then used to supply the most sensitive mirror voltage of the MR-ToF MS to significantly increase the short term and long-term mass resolving power of the apparatus.
Infrared laser absorption spectroscopy (IRLAS) employing both tuneable diode and quantum cascade lasers (TDLs, QCLs) has been applied with both high sensitivity and high time resolution to plasma diagnostics and trace gas measurements.
TDLAS combined with a conventional White type multiple pass cell was used to detect up to 13 constituent molecular species in low pressure Ar/H2/N2/O2 and Ar/CH4/N2/O2 microwave discharges, among them the main products such as H2O, NH3, NO and CO, HCN respectively. The hydroxyl radical has been measured in the mid infrared (MIR) spectral range in-situ in both plasmas yielding number densities of between 1011 ... 1012 cm-3. Strong indications of surface dominated formation of either NH3 or N2O and NO were found in the H2-N2-O2 system. In methane containing plasmas a transition between deposition and etching conditions and generally an incomplete oxidation of the precursor were observed.
The application of QCLs for IRLAS under low pressure conditions employing the most common tuning approaches has been investigated in detail. A new method of analysing absorption features quantitatively when the rapid passage effect is present is proposed. If power saturation is negligible, integrating the undisturbed half of the line profile yields accurate number densities without calibrating the system. By means of a time resolved analysis of individual chirped QCL pulses the main reasons for increased effective laser line widths could be identified. Apart from the well-known frequency down chirp non-linear absorption phenomena and bandwidth limitations of the detection system may significantly degrade the performance and accuracy of inter pulse spectrometers. The minimum analogue bandwidth of the entire system should normally not fall below 250 MHz.
QCLAS using pulsed lasers has been used for highly time resolved measurements in reactive plasmas for the first time enabling a time resolution down to about 100 ns to be achieved. A temperature increase of typically less than 50 K has been established for pulsed DC discharges containing Ar/N2 and traces of NO. The main NO production and depletion reactions have been identified from a comparison of model calculations and time resolved measurements in plasma pulses of up to 100 ms. Considerable NO struction is observed after 5 ... 10 ms due to the impact of N atoms.
Finally, thermoelectrically cooled pulsed and continuous wave (cw) QCLs have been employed for high finesse cavity absorption spectroscopy in the MIR. Cavity ring down spectroscopy (CRDS) has been performed with pulsed QCLs and was found to be limited by the intrinsic frequency chirp of the laser suppressing an efficient intensity build-up inside the cavity. Consequently the accuracy and advantage of an absolute internal absorption calibration is not achievable. A room temperature cw QCL was used in a complementary cavity enhanced absorption spectroscopy (CEAS) configuration which was equipped with different cavities of up to ~ 1.3 m length. This spectrometer yielded path lengths of up to 4 km and a noise equivalent absorption down to 4 x 10-8 cm-1Hz-1/2. The corresponding molecular concentration detection limit (e.g. for CH4, N2O and C2H2 at 1303 cm-1/7.66 μm) was generally below 1 x 1010 cm-3 for 1 s integration times and one order of magnitude less for 30 s integration times. The main limiting factor for achieving even higher sensitivity is the residual mode noise of the cavity. Employing a ~ 0.5 m long cavity the achieved sensitivity was good enough for the selective measurement of trace atmospheric constituents at 2.2 mbar.
(A paperback version is published by Logos under ISBN 978-3-8325-2345-9.)
Colossal magneto-resistance manganites are characterized by a complex interplay of charge, spin, orbital and lattice degrees of freedom. Formulating microscopic models for these compounds aims at meeting two conflicting objectives: sufficient simplification without excessive restrictions on the phase space. We give a detailed introduction to the electronic structure of manganites and derive a microscopic model for their low-energy physics. Focusing on short-range electron–lattice and spin–orbital correlations we supplement the modelling with numerical simulations.
Abstract
In this series of two papers we present results about the E-H transition of an inductively coupled oxygen discharge driven at radio frequency (13.56 MHz) for different total gas pressures. The mode transition from the low density E-mode to the high density H-mode is studied using comprehensive plasma diagnostics. The measured electron density can be used to distinguish between the different operation modes. This paper focuses on the determination of the negative atomic ion density and the electronegativity by two experimental methods and global rate equation calculation. As a result, the electronegativity significantly decreases over two orders of magnitude from about 25 in the E-mode to about 0.1 in the H-mode. The temporal behavior of the electronegativity in pulsed ICP shows that the negative atomic ion density reaches a steady state after 10 ms. Negative atomic ions are mainly produced by the dissociative attachment with the molecular ground state. The ion–ion recombination with the positive molecular ions and the collisional detachment with the singlet molecular metastables contribute significantly to the loss of the negative atomic ions.
Comprehensive study of the discharge mode transition in inductively coupled radio frequency plasmas
(2016)
In this contribution, the mode transition of an inductively coupled radio frequency plasma at low pressure is investigated. Therefore, a comprehensive set of plasma diagnostics were applied to determine plasma and processing parameters. Therewith, the plasma kinetics and especially the important elementary processes were studied. Hence, the reason for the mode transition was identified.
Abstract
In this series of two papers, the E-H transition in a planar inductively coupled radio frequency discharge (13.56 MHz) in pure oxygen is studied using comprehensive plasma diagnostic methods. The electron density serves as the main plasma parameter to distinguish between the operation modes. The (effective) electron temperature, which is calculated from the electron energy distribution function and the difference between the floating and plasma potential, halves during the E-H transition. Furthermore, the pressure dependency of the RF sheath extension in the E-mode implies a collisional RF sheath for the considered total gas pressures. The gas temperature increases with the electron density during the E-H transition and doubles in the H-mode compared to the E-mode, whereas the molecular ground state density halves at the given total gas pressure. Moreover, the singlet molecular metastable density reaches 2% in the E-mode and 4% in the H-mode of the molecular ground state density. These measured plasma parameters can be used as input parameters for global rate equation calculations to analyze several elementary processes. Here, the ionization rate for the molecular oxygen ions is exemplarily determined and reveals, together with the optical excitation rate patterns, a change in electronegativity during the mode transition.
Computational chemical physics can give important input to astrophysical modelling and other fields of physics, where molecular properties are of importance. Understanding of spectroscopic and reactive behaviour is crucial for many systems of astrophysical interests like stars, interstellar medium and comets. Especially stellar atmospheres are of interest, because the complex physics of stars are not yet completely understood. Stars are in an unstable balance of gravitation and radiation pressure and the atmospheric dynamics have been subject of extensive modelling. Complete and accurate spectroscopic information of the atoms and molecules in these atmospheres is necessary for this attempt. In addition, the only information we have about astrophysical systems is light which is emitted or absorbed by particles in these media. This is not only true for astrophysics. In plasma physics sometimes the usage of invasive diagnostics, like Langmuir probes, is not wanted because they disturb the system. In these cases some information of the system can be regained by passively measuring infrared spectra of the plasma or by active induction of electronic transition like the laser-induced fluorescence method. Another remote sensing application is the measurement of the atmospheric composition on earth. Here, larger particles in the atmosphere as well as greenhouse gases are of current interest. Unfortunately, the experimental spectroscopic data, which is needed for the understanding and interpretation of the measured spectra, is often incomplete. This gap can be, to some extend, filled by computational chemical physics. The aim of this work was to investigate the capabilities and limitations of ab initio based potential energy surfaces for spectroscopic and reactive studies and to apply these methods to problems of rovibrational and rovibronic spectroscopy and reaction dynamics. The choice of ab initio methods and the potential fitting methods is critical for the computational chemical physics, as all further quantities directly depend on their quality. In this work modified versions of the Braams polynomial potential energy surface were used. A high level coupled cluster ab initio method was used to build potentials for a series of small hydrocarbons. Hydrocarbons can be found almost everywhere on earth and in the universe. They exist in laboratory plasmas, stellar and planetary atmospheres and interstellar gases. In all these cases, light emitted or absorbed by the molecules is an important diagnostics of the system. The potential constructed in this work partly included a cluster expansion, which adds reactant configuration spaces to the fits. This could not be done for CH_3 and higher hydrocarbons, because of the limitations of the Coupled Cluster ab initio method, which is well suited for the potential wells, but not for the dissociation regions. The examples of methyl and methane show how the potentials can be used for rovibrational spectroscopy. Results of radiation transport simulations illustrate the importance of as complete-as-possible line lists for radiation transport calculations.\\ The rovibronic spectroscopy of diatomic molecules is another important aspect for the stellar atmospheric modelling. Metal hydrides and oxides add opacity to the atmosphere in the visible light and ultraviolet frequency regions, as well as do the hydrocarbons in the infrared one. In addition the spectra of metal hydrides/oxides can be used to gather information about metal and their isotope abundances. They are used as markers for the conditions in the atmospheres of stars. In this work a new code was developed, that efficiently calculates bound-bound transitions between electronic states and bound-continuum cross sections for diatomic molecules. It also offers an adequate treatment of quasi-bound rovibrational states. One important representative of the diatoms is magnesium hydride, MgH. Before this work, line lists and photodissociation cross section were available involving the three lowest doublet states of MgH. In this work new potential energy curves were calculated and adapted to updated experimental data. This causes changes in the relative energies between the electronic states and therefore shifts in the line lists. These are important, because accurate line positions are needed for the identification of spectral lines. In addition two further electronic states were included in the calculations. This expands the spectral range of MgH into the near ultraviolet region. Radiation transport models showed significant absorption by MgH from the newly added electronic states. A second usage of the diatomic potential energy curves are photodissociation cross sections. As interstellar environments are chemically active, such data is necessary for a complete picture of the ongoing processes. The photodissociation cross sections of MgH reveal a stronger dependence of the underlying potential than the bound-bound lines. In the case of MgH the cross sections are rather weak, besides occasional resonance lines which can be several orders of magnitude stronger. As mentioned, not only spectroscopic, but also reactive behaviour of molecules is important in astrophysics. A current problem connected with this is the abundance of CH^+ in interstellar clouds. Its measured abundances do not fit the predictions from theoretical models. In addition Gerlich and co-workers recently measured low temperature H + CH^+ -> C^+ + H_2 reaction rates, which diverge from the theoretical picture and which could not be explained. In this work a reactive potential energy surface was built for the CH_2^+ system, which was then used to perform extensive calculations with quasi-classical trajectory and quantum scattering methods. It was found out, that the potentials used in previous works are not accurate enough to allow low temperature calculations. Results from these potentials must be taken with care. Furthermore, the results from the new potential energy surface indicate significantly reduced reaction rates compared to previous numerical studies. This is in agreement with the new results of Gerlich and co-workers. Nevertheless, the large error bars in the low temperature range for experimental as well as numerical results strongly suggest refined methods to be developed for both, before a final conclusion can be made. This work demonstrated the possibility of modern computational chemical physics to supply consistent data for spectroscopy and reaction dynamics. These are necessary and important inputs for fields like astrophysics, plasma physics and chemistry.
Advancing Radiation-Detected Resonance Ionization towards Heavier Elements and More Exotic Nuclides
(2022)
RAdiation-Detected Resonance Ionization Spectroscopy (RADRIS) is a versatile method for highly sensitive laser spectroscopy studies of the heaviest actinides. Most of these nuclides need to be produced at accelerator facilities in fusion-evaporation reactions and are studied immediately after their production and separation from the primary beam due to their short half-lives and low production rates of only a few atoms per second or less. Only recently, the first laser spectroscopic investigation of nobelium (Z=102) was performed by applying the RADRIS technique in a buffer-gas-filled stopping cell at the GSI in Darmstadt, Germany. To expand this technique to other nobelium isotopes and for the search for atomic levels in the heaviest actinide element, lawrencium (Z=103), the sensitivity of the RADRIS setup needed to be further improved. Therefore, a new movable double-detector setup was developed, which enhances the overall efficiency by approximately 65% compared to the previously used single-detector setup. Further development work was performed to enable the study of longer-lived (t1/2>1 h) and shorter-lived nuclides (t1/2<1 s) with the RADRIS method. With a new rotatable multi-detector design, the long-lived isotope 254Fm (t1/2=3.2 h) becomes within reach for laser spectroscopy. Upcoming experiments will also tackle the short-lived isotope 251No (t1/2=0.8 s) by applying a newly implemented short RADRIS measurement cycle.
Multiply negatively charged aluminium clusters and fullerenes were generated in a Penning trap using the "electron-bath" technique. Aluminium monoanions were generated using a laser vaporisation source. After this, two-, three- and four-times negatively charged aluminium clusters were generated for the first time. This research marks the first observation of tetra-anionic metal clusters in the gas phase. Additionally, doubly-negatively charged fullerenes were generated. The smallest fullerene dianion observed contained 70 atoms.
Explosive volcanic eruptions emitting large amounts of sulfur can alter the temperature of the lower stratosphere and change the circulation of the middle atmosphere. The dynamical response of the stratosphere to strong volcanic eruptions has been the subject of numerous studies. The impact of volcanic eruptions on the mesosphere is less well understood because of a lack of large eruptions in the satellite era and only sparse observations before that period. Nevertheless, some measurements indicated an increase in mesospheric mid-latitude temperatures after the 1991 Pinatubo eruption. The aim of this study is to uncover potential dynamical mechanisms that may lead to such a mesospheric temperature response. We use the Upper-Atmospheric ICOsahedral Non-hydrostatic (UA-ICON) model to simulate the atmospheric response to an idealized strong volcanic injection of 20 Tg S into the stratosphere (about twice as much as the eminent 1991 Pinatubo eruption). Two experiments with differently parameterized effects of sub-grid-scale orography are compared to test the impact of different atmospheric background states. The simulations show a significant warming of the polar summer mesopause of up to 15–21 K in the first November after the eruption. We argue that this is mainly due to intrahemispheric dynamical coupling in the summer hemisphere and is potentially enhanced by interhemispheric coupling with the winter stratosphere. This study focuses on the first austral summer after the eruption because mesospheric temperature anomalies are especially relevant for the properties of noctilucent clouds, whose season peaks around January in the Southern Hemisphere.