The kinetics of energetic O− ions in discharge H2O plasma

Abstract

Using Monte Carlo simulation, the translational relaxation of energetic O− ions produced by dissociative electron attachment to molecules was studied in water vapor plasmas in a strong electric field. Initial O− ions are energetic and are more reactive than the ions being in equilibrium with the electric field. Because of this, the energetic O− ions have a chance to be involved in endothermic reactions prior to energy relaxation of these ions. The probabilities of charge exchange and electron detachment in ion-molecule interactions were calculated versus the reduced electric field. It was shown that several percent of energetic O− ions produced in water vapor plasma by dissociative electron attachment to H2O molecules are rapidly transformed to OH− ions due to charge exchange collisions or are decomposed to release free electrons. The total probability of charge exchange and electron detachment from energetic O− ions increases up to around 90% when these ions are produced by dissociative electron attachment to O2 molecules if oxygen is added to water vapour. This means that, in this case, most of energetic ions formed from O2 molecules are involved in charge exchange and electron detachment reactions prior to their thermalization.