Bulletin of the American Physical Society
64th Annual Gaseous Electronics Conference
Volume 56, Number 15
Monday–Friday, November 14–18, 2011; Salt Lake City, Utah
Session PR1: Plasma Chemistry |
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Chair: Jan Benedikt, Ruhr University Bochum Room: 255D |
Thursday, November 17, 2011 2:00PM - 2:30PM |
PR1.00001: Correlating Gas-Phase Energetics of Plasma Radicals with Surface Interaction Data Invited Speaker: Understanding how energy is distributed within a plasma and the specific contributions of gas-phase species to plasma processing is key to understanding the chemistry that leads to specific surface modifications. The surface interactions of gas-phase plasma species provide critical molecular level information on plasma processing, especially at interfaces. Clearly, power dissipation and energetics are also important for elucidation of mechanistic details in plasmas. The imaging of radicals interacting with surfaces (IRIS) technique uses laser-induced fluorescence to provide spatially-resolved images of plasma species and direct information on the energetics of plasma-generated and surface-scattered radicals. Combined with optical emission spectroscopy, we have measured the internal and translational temperatures for a range of species in several plasma environments. This work concentrates on NO, SiF, and CF radicals in a range of plasmas, although comparisons to other radicals will also be made. For many of these molecules, vibrational temperatures are significantly higher than rotational temperatures and energy partitioning is correlated to surface reactivity. The gas-phase data are complemented by materials analysis data that reveal a more detailed picture of the overall plasma process. [Preview Abstract] |
Thursday, November 17, 2011 2:30PM - 2:45PM |
PR1.00002: Chemical kinetics of radio-frequency driven atmospheric-pressure helium-oxygen plasmas in humid air Tomoyuki Murakami, Kari Niemi, Timo Gans, Deborah O'Connell, William Graham We describe the chemical kinetics of radio-frequency (rf) driven atmospheric-pressure helium-based plasmas in ambient air as determined through a zero-dimensional time-dependent global model. The effects of humid-air admixtures on the plasma-induced chemical reactions and the evolution of species concentrations in the helium-oxygen mixture (He-O2, helium with 5000 ppm admixture of oxygen) are studied for wide air impurity levels of 1-5000 ppm with the relative humidity of 0-100\%. Comparisons made with experiments using an rf driven micro-scale atmospheric pressure plasma jet and one-dimensional simulations suggest that the plausible air impurity level in the experiments is not more than hundreds ppm. Effects of the air impurity containing water-humidity on electro-negativity and chemical activity are clarified with particular emphasis on reactive oxygen species. [Preview Abstract] |
Thursday, November 17, 2011 2:45PM - 3:00PM |
PR1.00003: Measurement of OH density and mixture ratio of ambient air in atmospheric pressure helium plasma jet using laser induced fluorescence Seiya Yonemori, Nakagawa Yusuke, Ryo Ono, Tetsuji Oda Atmospheric pressure helium plasma jet is getting much attention especially in plasma medical application field because of its extreme low heat load. In this plasma, active species are generated by the reaction of plasma with ambient air. However, the density of active species generated by that plasma jet has not been sufficiently measured. OH radical is one of the most important active species because it plays important role in many plasma processes including plasma medicine. In this study, the density of OH density and mixture ratio of ambient air in atmospheric pressure helium plasma jet were measured by using laser induced fluorescence (LIF) method. Mixture ratio of ambient air in the plasma jet was obtained from the decay time of LIF signal of OH radicals. It clearly showed the penetration of the ambient air into the helium plasma jet. This mixture of helium plasma jet with the ambient air is important because various radicals such as OH and O are produced in this mixture region. The OH density was about 2.5 ppm at the center axis of the plasma plume when AC 5 kV applied. It reduced with increasing distance from the nozzle. [Preview Abstract] |
Thursday, November 17, 2011 3:00PM - 3:15PM |
PR1.00004: Effect of vibrationally excited molecules on the production of O radicals in a pulsed streamer discharge Atsushi Komuro, Ryo Ono, Tetsuji Oda Streamer discharge is widely used in many applications. However, the understanding of its phenomena is still poor. The complete simulation of the streamer discharge can lead to a better understanding of the physical-chemical activity and help us to choose the best operating conditions. The vibrationally excited molecules have large influence on the discharge phenomenon. In atmospheric pressure plasma, the vibrationally excited molecules affect the dissociative attachment (e + O$_{2} \quad \to $ O + O$^{-})$ because the survival probability of intermediate negative ions (e.g. O$_{2}^{-\ast }$ ) between auto-ionization and dissociation strongly depends on vibrational state. Atomic oxygen is one of the important radicals in plasma. We previously measured the O radical density and showed that O radicals are mainly produced in the secondary streamer channels, not in the primary streamer channels. However, it has not been numerically reproduced yet because the vibrational kinetics in atmospheric pressure plasma has not been sufficiently considered. In this research, we developed two-dimensional numerical modeling of the cathode directed streamer in air including vibrational kinetics. The obtained results showed that vibrationally excited molecules have large influence on the production rate of O radicals in the streamer discharge. [Preview Abstract] |
Thursday, November 17, 2011 3:15PM - 3:30PM |
PR1.00005: ABSTRACT WITHDRAWN |
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