Positive dc corona between coaxial electrodes in mixtures of carbon dioxide and oxygen

The positive corona discharge has been generated in a reactor equipped with a system of stainless steel cylindrical coaxial electrodes. The discharge has been fed with mixtures of carbon dioxide and oxygen (0–100% of oxygen) in flow-stopped regime. The time dependence of discharge current has been measured for a period of 1 h. The effect of the mixture composition on the discharge current and the onset voltage of the discharge has been investigated. A slight increase in the onset voltage was observed with increasing amount of oxygen in the gas mixture up to 20% of oxygen, where the maximum was reached. Then, with further increase of oxygen concentration, the onset voltage decreased. These results correspond to the measured discharge currents. The lowest currents were observed for a mixture containing 20% of oxygen, where the onset voltage is highest, and the highest currents were observed for pure oxygen, where the onset voltage is lowest. These observations are in agreement with Townsend's formula expressing the current–voltage characteristics of the discharge

Dissociative electron attachment to HBr: A temperature effect

The effects of rovibrational temperature on dissociative electron attachment to hydrogen bromide has been investigated from the experimental and theoretical point of view. Theoretical calculations based on the nonlocal resonance model predict a strong temperature effect on the Br⁻ fragment ion yield due to population of higher vibrational and rotational states. A crossed beam experimental setup consisting of a temperature controlled effusive molecular beam and a trochoidal electron monochromator has been used to confirm this prediction. The high degree of agreement between experiment and theory indicates the validity of the theoretical model and its underlying physical picture

Experimental study of negative corona discharge in pure carbon dioxide and its mixtures with oxygen

The products of a negative corona discharge in both pure CO2 and mixtures of CO2 + O2 have been studied using a coaxial cylindrical electrode geometry with particular emphasis on the production of ozone. The discharge current in pure CO2 was found to be highly sensitive to the presence of trace concentrations of molecular oxygen and to changes in the flow speed through the discharge. The effect of dissociative electron attachment to ozone on the discharge current was studied by measurements of ozone and CO production. The ozone concentration increases monotonically with increasing content of oxygen in the mixture with carbon dioxide, whereas the CO concentration exhibits a flat maximum for oxygen concentrations of around 4%. A simple kinetic model of the dominant chemical processes is described and compared with the experimental results