High-energy collision keV

The technique consists of introducing a gas into the collision cell as a molecular beam directed perpendicularly to the ion beam accelerated by a potential of a few kilovolts towards an outlet where a pump removes it from the instrument so as to preserve a vacuum compatible with the use of electromagnetic analysers. This collision cell is located at a focal point to avoid losses. It is better to float the collision cell electrically to distinguish the metastable from the CID products. 

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FIGURE 9. Reactions of chlorobenzene radical cations with ammonia (a) mass spectrum of the ions produced within the quadrupole collision cell (the intensity of the m/z 112 peak is reduced by a factor of 25), and (b) high energy (8 keV, nitrogen collision gas) of the so-produced m/z 94 ions. Spectrum (c) corresponds to the reactions of the m/z 11 phenyl cation, formed in the ion source, with ammonia (the intensity of the m/z 77 peak is reduced by a factor of 40)... 

Assumption (a) is appropriate for violent collisions. Violent collisions between atoms of reasonably high energy range (keV) require the collision partners to approach very closely, so that the probability of a collision between three or more atoms is small. Soft collisions can take place at large distances and therefore can involve more than two atoms simultaneously. However, soft collisions usually can be treated by perturbation theory (the momentum or impulse approximation), in which case no restriction to binary collisions is necessary. At lower energies (below 1 keV), collective effects become increasingly important and assumption... 

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