Abstract: This dissertation presents novel results in the study of nanosecond pulsed, non-equilibrium plasmas. Specifically, an in-depth experimental study of the role of atomic oxygen on the kinetic mechanisms involved in three distinct discharge geometries was conducted. First, a low temperature (~300 K) and low pressure (

The first research on plasma was done in connection with the study of electrical discharges in gases. The focus of attention for physicists was the partially ionized plasma, the kinetics of which is governed by various collisional and radiative processes. The choice of this area of research was motivated largely by the practical problems of that time the creation of gas-discharge light sources, rectifiers, and inverters. Since the early 1950s interest in plasma physics has risen sharply, particularly in the study of the completely ionized plasma with its various collective phenomena, insta bilities, and the interesting and sometimes unexpected effects attending the propagation of electromagnetic waves in such a plasma and the action on it of external electric and magnetic fields. Interest in hot plasmas has been stimulated not only by the diverse and novel physical phenomena, but also by the problems arising in connection with controlled nuclear fusion. The advent, in the early 1960s, of new technical fields such as gas-discharge lasers, magnetohydrodynamic generators, thermoemission converters, plasma chemistry, plasma propul sion devices, various methods in plasma technology, etc. , has led to increased interest in weakly ionized low-tempera ture plasmas. This is particularly true of nonequilibrium plasmas, which are characterized by an extraordinary diver sity of states and properties.

This is a comprehensive textbook designed for graduate and advanced undergraduate students. Both authors rely on more than 20 years of teaching experience in renowned Physics Engineering courses to write this book addressing the students’ needs. Kinetics and Spectroscopy of Low Temperature Plasmas derives in a full self-consistent way the electron kinetic theory used to describe low temperature plasmas created in the laboratory with an electrical discharge, and presents the main optical spectroscopic diagnostics used to characterize such plasmas. The chapters with the theoretical contents make use of a deductive approach in which the electron kinetic theory applied to plasmas with basis on the electron Boltzmann equation is derived from the basic concepts of Statistical and Plasma Physics. On the other hand, the main optical spectroscopy diagnostics used to characterize experimentally such plasmas are presented and justified from the point of view of the Atomic and Molecular Physics. Low temperature plasmas (LTP) are partially ionized gases with a broad use in many technological applications such as microelectronics, light sources, lasers, biology and medicine. LTPs lead to the production of atomic and molecular excited states, chemically reactive radicals, and activated surface sites, which are in the origin, among others, of the deposition of thin films, advanced nanotechnology products, solar cells, highly efficient combustion motors, and treatment of cancer cells.

Abstract: The dissertation presents non-equilibrium chemical kinetic studies of large volume lean gaseous hydrocarbon/ air mixture combustion at temperatures (~300K) much below self ignition temperatures and low pressures (40-80torr), in ~25 nanosecond duration repetitive high voltage (~18kV) electric discharges running at 10 Hz. Xenon calibrated Two Photon Absorption Laser Induced Fluorescence (TALIF) is used to measure absolute atomic oxygen concentrations in air, methane-air, and ethylene-air non-equilibrium plasmas, as a function of time after initiation of a single 25 nsec discharge pulse at 10Hz. Oxygen atom densities are also measured after a burst of nanosecond discharges at a variety of delay times, the burst being run at 10Hz. Each burst contains sequences of 2 to 100 nanosecond discharge pulses at 100 kHz. Burst mode measurements show very significant (up to ~0.2%) build-up of atomic oxygen density in air, and some build-up (by a factor of approximately three) in methane-air at [phi]=0.5. Burst measurements in ethylene-air at [phi]=0.5 show essentially no build-up, due to rapid O atom reactions with ethylene in the time interval between the pulses. Nitric oxide density is also measured using single photon Laser Induced Fluorescence (LIF), in a manner similar to oxygen atoms, and compared with kinetic modeling. Fluorescence from a NO (4.18ppm) +N2 calibration gas is used to calibrate the NO densities. Peak density in air is found to be ~ 3.5ppm at ~ 225us, increasing from almost initial levels of ~ 0 ppm directly after the pulse. Kinetic modeling using only the Zeldovich mechanism predicts a slow increase in NO formation, in ~ 2 ms, which points towards the active participation of excited N2 and O2 molecules and N atoms in forming NO molecules. Ignition delay at a variety of fuel/ air conditions is studied using OH emission measurements at ~ 308nm as ignition foot prints. The ignition delay is found to be in the range of 6-20ms for ethylene/ air mixtures. No ignition was observed in the case of methane/ air mixtures. All these measurements agree well with kinetic modeling developed involving plasma reactions and electron energy distribution function calculations.

The first research on plasma was done in connection with the study of electrical discharges in gases. The focus of attention for physicists was the partially ionized plasma, the kinetics of which is governed by various collisional and radiative processes. The choice of this area of research was motivated largely by the practical problems of that time the creation of gas-discharge light sources, rectifiers, and inverters. Since the early 1950s interest in plasma physics has risen sharply, particularly in the study of the completely ionized plasma with its various collective phenomena, insta bilities, and the interesting and sometimes unexpected effects attending the propagation of electromagnetic waves in such a plasma and the action on it of external electric and magnetic fields. Interest in hot plasmas has been stimulated not only by the diverse and novel physical phenomena, but also by the problems arising in connection with controlled nuclear fusion. The advent, in the early 1960s, of new technical fields such as gas-discharge lasers, magnetohydrodynamic generators, thermoemission converters, plasma chemistry, plasma propul sion devices, various methods in plasma technology, etc. , has led to increased interest in weakly ionized low-tempera ture plasmas. This is particularly true of nonequilibrium plasmas, which are characterized by an extraordinary diver sity of states and properties.

Emphasis is placed on the analysis of translational, rotational, vibrational and electronically excited state kinetics, coupled to the electron Boltzmann equation.

Kinetics and Spectroscopy of Low Temperature Plasmas derives in a full self-consistent way the electron kinetic theory used to describe low temperature plasmas created in the laboratory with an electrical discharge, and presents the main optical spectroscopic diagnostics used to characterize such plasmas. The chapters with the theoretical contents make use of a deductive approach in which the electron kinetic theory applied to plasmas with basis on the electron Boltzmann equation is derived from the basic concepts of Statistical and Plasma Physics. On the other hand, the main optical spectroscopy diagnostics used to characterize experimentally such plasmas are presented and justified from the point of view of the Atomic and Molecular Physics.