Three-body attachment

1 In conventional electron-impact ion sources, the rate of production 

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Three-body attachment of electrons seems to provide a more attractive explanation. Several reactions are worthy of consideration ... 

Substituting the appropriate concentrations (noH 1015 cm.-3) gives kz 10-31 cm.6 molecule-2 sec.-1 This is less than the recommended value by one order of magnitude, and three-body attachment of electrons to OH thus appears to provide a reasonable reaction path by comparison, Reactions 7 and 8 also seem reasonable. 

Table 1 Three-Body Attachment Rate Constants /cm for the Reaction e Room Temperature (From Refs. 10 and 11.)...

In later PR-TRMC measurements, the after-pulse relaxation of the microwave conductivity itself in pure gases was monitored with nanosecond time-resolution and this provided a more detailed, quantitative method of monitoring electron thermalization. Of particular importance was a detailed study of thermalization in helium, which could be used to test the predictions of different theoretical treatments for this well-characterized gas. Detailed thermalization data were also obtained for oxygen, for which the concurrent three-body attachment process provides an interesting complication. The dramatic influence of small concentrations of water vapor on the thermalization process was also demonstrated for samples of dry and humid air. ° The (unexpectedly) high thermalization... 

Electrons can also be lost through attachment to form negative ions in those gases for which stable negative ions exist. Three-body attachment,... 

Atmospheric-pressure non-thermal discharges in air are probably the most important systems, where the three-body attachment plays a key role in the balance of charged particles ... 

Three-body attaehment Rate coefficient Three-body attachment Rate coefficient... 

Slowing down of ionizing electrons (three-body attachment) ... 

Negative ions for use as reactants in ion-neutral reactions are usually prepared by dissociative electron attachment, three-body attachment, or ion-pair production. Other techniques available include radiative attachment and surface reactions. Finally, some negative ions can be formed most efficiently by ion-neutral reactions themselves. The following discussion of these processes is intended only to be illustrative, and references are made principally to review articles. 

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