Plasma-chemical reaction positive ions

ELEMENTARY PLASMA-CHEMICAL REACTIONS OF POSITIVE IONS... 

Elementary Plasma-Chemical Reactions of Positive Ions... 

Positive ions are obvionsly major players in plasma-chemical processes. Their exothermic reactions with neutrals usually have no activation energy, which makes their contribution significant in many specific plasma-chemical processes, particularly in plasma catalysis. In addition to high chemical activity, the ions can have significant kinetic eneigy, which determines their contribntion, for example, in reactive ion etching. 

Some ion-molecular reactions were already discussed earlier. Thus, the positive ion conversion A+ -I- B -I- M AB+ + M was considered in Section 2.2.2 as a preliminary stage of the dissociative electron-ion recombination. Ion-molecular reactions not only make a contribution in the balance of charged particles but also provide plasma-chemical processes by themselves. Ion-cluster growth in dusty SiH4 plasmas and ion-molecular chain reactions of SO2 oxidation in air during exhaust gas cleaning are good relevant examples, which will be discussed later in the book. 

Plasma is produced by applying energy to a gas fot instance, when a high voltage is applied between two electrodes, the gas molecules ate broken down into electrons and positive ions. The acceleration of electrons and theit subsequent colHsion with othet particles induces ionization, excitation, and fragmentation ptocesses of molecules. These ptocesses lead to a complex mixture of active species, which, under the effect of electtic and/ot magnetic fields, take part in chemical reactions and interact with sutfaces. 

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