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Experiments on the plasma-assisted oxidation of dilute concentrations of acetone, benzene, and ethylene in atmospheric pressure gas streams by pulsed corona electrical discharge processing show that temperature influences the oxidation chemistry. In dry air mixtures, the main oxidation products are CO and CO2, which account for most if not all of the oxidized acetone and benzene. Plasma-assisted oxidation of ethylene is less complete since the measured CO and CO2amounts do not account for the decrease in ethylene. The energy efficiency for plasma-assisted oxidation of ethylene is also less temperature dependent than that for either acetone or benzene. These trends correlate with the temperature dependence in the rate constant expressions for reactions of these molecules with O atoms.

This paper presents a comparative assessment of the energy efficiencies of pulsed corona and electron beam methods for processing of dilute concentrations of hazardous air pollutants in atmospheric-pressure dry air streams. The four representative compounds investigated are ethylene, o-xylene, toluene and benzene. It is shown that the electron beam method requires much less electrical energy than the pulsed corona method to achieve the same level of pollutant decomposition. The results imply that the initial decomposition of these pollutant molecules is achieved more efficiently through reactions with either electrons or ions, rather than through oxidation by O radicals.

Electromagnetic plasma computer simulations are used to analyze the frequency shifts caused by the ionization of atmospheric-density noble gases during interaction with intense femtosecond laser pulses; the results are presented and compared with experimental data. The simulations trace the temporal evolution of plasma growth during the femtosecond ionizing pulse and calculate the resulting self-induced blue shift of the ionizing pulse spectrum. Variations with pulse intensity, gas pressure, and gas species are calculated. The relative contributions of strong-field ionization and electron-impact ionization on the frequency shifts are discussed. The simulations provide qualitative explanations of most of the features observed experimentally in the blue-shifted spectra. The technique of spectral blue shifting intense femtosecond laser pulses provides a new diagnostic tool for studying strong-field ionization and laser-induced breakdown in dense plasmas.

Experimental results on the chemical reduction of dilute concentrations of NO2in N2by pulsed corona and dielectric-barrier discharge processing axe presented. The initial reduction of NO2proceeds via N + NO2→ N2O + O. The subsequent reduction of NO2then proceeds via O + NO2-► NO + O2, followed by N + NO → N2 + O; the latter reaction reproduces O radicals to initiate the next NO2reduction cycle.