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Showing 1 to 20 of 34 for “"Negative Ions"”.
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Excited States in Negative Ions
This thesis covers experimental studies of atomic negative ions with the main goal of increasing our fundamental understanding of these fragile quantum systems. Comparisons of measurements and calculations have been used to increase our understanding of these highly correlated, yet simple, systems. …
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STABILITY AND SPECTROSCOPIC PROPERTIES OF NEGATIVE IONS
Negative ions play an important role in chemistry as building blocks of salts and oxidizing agents. Halogen atoms, due to their ability to attract electrons, readily form negative ions. Considerable interest exists in the design and synthesis of new negative ions called superhaogens whose electron …
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Effects of Anion Excited States on Photodetachment of Negative Ions
… of anion excited states on photodetachment of negative ions containing transition metals will be presented. Evidence of autodetachment (sudden change in photodetachment cross section and photoelectron agular distribution) is observed for diatomic (AgF<super>-</super>, CuF<super>-</super>) and …
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Photodetachment Studies of Atomic Negative Ions Through Velocity-Map Imaging Spectroscopy
… spectroscopy as been adapted to a keV-level negative ion beamline for studies of photon-negative ion collisions. The design and operation of the VMI spectrometer takes into consideration the use of continuous, fast-moving (5 keV to 10 keV) ion beams, as well as a continuous wave (CW) laser as …
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Etude par Spectrométrie de Masse de la formation d'Ions Négatifs par Attachement Electronique Dissociatif et par le processus de Paire d'Ions.
… of this work is to investigate the appearance of negative ions by both the mechanism of Dissociative Electron Attachment (DEA) and Ion Pair processes (IPP) by electron impact. Using the appropriate instrumentation (a conventional Nier type mass spectrometer) the best conditions are chosen to …
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Enhancement of the Negative Ion Flux to Surfaces From Radio-Frequency Processing Discharges
The relative flux of negative ions from rf discharges through CF$\sb4$ and F$\sb2$-He has been studied using mass spectrometry. The negative ion flux impinging on a surface in contact with a glow discharge is usually quite small because of the sheaths formed to contain the more mobile electrons. In …
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Numerical and Experimental Study of the Trichel Pulses in Needle-plane Geometry
One of the unique aspects of the negative corona discharges in the air is the regular train of pulses that form the discharge current, called Trichel pulses. These pulses are the result of the combination of several phenomena such as the avalanche ionization of the neutral molecules by the impact …
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Simulation of Transients and Transport in Plasma Processing Reactors
… transients during pulsed operation, energetic negative ions can be extracted from pulsed ICPs that can aid in reducing charge buildup on wafers. Energetic negative ions can be extracted from Ar/Cl2 pulsed ICPs with pulsed low frequency (1--2 MHz) substrate biases. Employing the 3D model, the …
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Impulse breakdown characteristics of SF6 and its mixtures in highly non-uniform field gaps
… fields can exist in GIS under certain conditions as, for example, when a needle-like free metallic particle is attracted to the inner conductor or is deposited on the surface of an insulator. Such defects can result in very low breakdown levels and, with large defects (e.g. particles several …
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Modeling and Simulation of Charged Species in Lean Methane-Oxygen Flames
… systems. Chemical pathways which involve ions are known to contribute to the formation of air pollutants like soot and aerosols. The appearance of electrical charges, which are closely related to the combustion process itself, offers the opportunity of their use for sensing purposes in a …
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Modeling of generation and transport of particles in low pressure glow discharges and contamination of wafers
… and can perturb electron transport. The role of negative ions in the formation of large clusters, the precursors to particles, in low pressure plasmas is theoretically investigated. We find that the formation of particles requires a critically large cluster. We propose that negatively charged …
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Plasma Dynamics in a High-Power Helicon Source
… over 100 million kelvin to sustain fusion reactions. Neutral Beam Injectors (NBIs) will provide most of the heating power by accelerating negative ions to energies of 1 MeV, where they are then neutralised to penetrate the magnetic confinement fields. Negative ions, as opposed to positive ions, …
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Plasma Dynamics in a High-Power Helicon Source
… over 100 million kelvin to sustain fusion reactions. Neutral Beam Injectors (NBIs) will provide most of the heating power by accelerating negative ions to energies of 1 MeV, where they are then neutralised to penetrate the magnetic confinement fields. Negative ions, as opposed to positive ions, …
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Laser spectroscopy of molecular ions in an ion beam
… ion beam is overlapped by a laser beam and the ions are Doppler-tuned into resonance. The experimental apparatus is suitable for the study of both positive and negative ions. Resonant transitions are reported in C{dollar}\sb2\sp{-}{dollar} and in CO{dollar}\sp{+}{dollar}. In …
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ELECTROSTATIC (LANGMUIR) PROBE MEASUREMENTS IN RF DRIVEN He, N2, BCl3, AND BCl3/N2 PLASMAS
… and 3.69 eV @ 60% N2). However, an increase in negative ion density was observed with nitrogen addition reaching a maximum at 40% N2. Although negative ions play no role in etching, this trend seems to correlate with the observed etch rate enhancement. A plausible explanation for both the …
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Surface Acoustic Wave Nebulization as a Mass Spectrometry Ionization Source, Characterization and Application
… describes a novel method to generate ions for mass spectrometers that simplifies the operation and decreases the internal energy distribution of ions. The surface acoustic wave nebulization (SAWN) is a nebulization method generating both positive and negative ions from liquid phase. We …
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Ion-molecule reaction mass spectrometry and vacuum-ultraviolet negative photoion spectroscopy
… spectrometry has been used to study the reactions of cations and anions with ethene, monofluoroethene, 1,1-difluoroethene, trifluoroethene and tetrafluoroethene. Calculated collisional reaction rate coefficients are compared to those measured by the experiment. The product ions from these …
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An Electron Target for Collision Experiments with Trapped Ions
… Target for Collision Experiment with Trapped Ions An experiment to study electron collisions on stored molecular ions has been built within the framework of this thesis. Ions are stored in a trap with a kinetic energy of several keV between two electrostatic mirrors. The stored ions are …
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Plasma Diagnostics of Discharges in Nitrogen-Trifluoride (Etching, Semiconductor)
… NF(,3) can be quite large, greater than 50%. The negative ion density in the NF(,3) plasma was determined by photodetaching the electrons from the negative ions and measuring the photodetached electron density with microwave interferometry. The steady state negative ion density was found to be 50 …
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Signal variation in single particle aerosol mass spectrometry
… uncertainties, resulting in shot-to-shot variations in the mass spectra. I found that the variations in mass peak areas in BAMS spectra were significantly larger than those predicted by Poisson statistics based on the mean number of detected ions. Furthermore, these variations were surprisingly …
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