Plasma Physics

1
Plasma Physics Engineering

• Lecture 6

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THE ION-MOLECULAR REACTIONS.

• This is another group of fast processes taking
  place in collisions of heavy particles.
• Some briefly discussed
• The positive ion-conversion A B M ? AB
  M, was considered as a preliminary stage of the
  dissociative electron-ion recombination.
• Clusterization of negative ions, using important
  examples of the formation of stable complex ions
  from a negative oxygen ion O-
• The fast ion-molecular reactions, as discussed,
  make an important contribution in the balance of
  charged particles. These also can provide
  plasma-chemical processes by themselves.

3
Ion-Molecular Polarization Collisions, the
Langevin Rate Coefficient.

• If a neutral particle itself has no permanent
  dipole moment, the ion-neutral charge-dipole
  interaction and scattering is due to the dipole
  moment pm , induced in the neutral particle by
  the electric field E of an ion
• (2.81)

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typical orbits of relative ion and neutral motion
during polarization scattering

• when the impact parameter is high, the orbit has
  a hyperbolic character
• when the impact parameter is sufficiently low,
  the scattering leads to the Langevin polarization
  capture.
• the spiral trajectory results in closer
  interaction and formation of the ion-molecular
  complex, which then can either spiral out or
  provide inelastic changes of state and formation
  of different secondary products.

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• ion-molecular capture process based on
  polarization occurs when
• O( )
• From this qualitative equality,?Langevin Cross
  Section
• Langevin capture rate coefficient
• ?f(T)
• rewrite