大気中コロナ放電によるイオンの生成と発展の研究

概要

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Ambient corona discharge has been used as an ionizer in a wide range of research and industrial fields such as environmental, analytical and aerosol sciences, and possibly even commercial electric appliances. Terminal ions produced via ion evolutions through successive ion-molecule reactions in corona discharge can readily and efficiently supply the charge for ionization in ambient air. Despite substantial progress in the application of corona discharge, the elementary processes involved in terminal ion formation and evolution are not yet well understood. It has been reported that negative ion evolution is rather complex compared to that of positive ions, and that it is difficult to regulate the reproducible formation of specific negative ion species. We have recently established an atmospheric pressure corona discharge system containing a specific corona needle that successfully leads to regular and reproducible generation of various positive and negative ions originating from ambient air. The system coupled with mass spectrometers made it possible to study the relationship between terminal ion formation and discharge conditions. In this paper, the formation and evolution mechanism of terminal ions such as H3O+, HO-, NOx- and COx- depending on the electric field strength on the needle tip and the resulting kinetic energy of electrons accelerated at the tip will be described.