electonIonization

Electron Ionization

Works with a VSimPD license. Collision of the form

\[A + e \rightarrow A^+ + e + e\]

An ionization process similar to Impact Ionization, but optimized for the specific case where an electron ionizes a second species.

In this collision, the energy of the scattered electron (that is, the final energy of the incident electron) is determined from:

\[\epsilon_{sc} = \epsilon_{inc} - \epsilon_{iz} - \epsilon_{se}\]

where:

  • \(\epsilon_{inc}\) the relative energy of the two reactants in center of mass frame
  • \(\epsilon_{iz}\) the ionization energy threshold
  • \(\epsilon_{se}\) the secondary electron energy which is given by:
\[\epsilon_{se} = \omega \tan \left[ R_3 \tan ^{-1} \left( \frac{ \epsilon_{inc} -\epsilon_{iz} }{2 \omega } \right) \right]\]

where \(\omega\) is a constant with a value of 15 eV and \(R_3\) is a random number with a uniform distribution between 0 and 1.

The trajectory of the scattered electron after the collision is determined by the scattering angle \(\chi\) such that:

\[\cos \chi = \left( \frac{\epsilon_{sc} }{ \epsilon_{inc} - \epsilon_{iz}} \right)^{0.5}\]

and the azimuthal angle \(\varphi = 2 \pi R_1\) , where \(R_1\) is a random number uniformly distributed between 0 and 1.

The scattering angle of the secondary electron (created in the interaction) is determined using:

\[\cos \chi_{sc} = \left( \frac{\epsilon_{se} }{ \epsilon_{inc} - \epsilon_{iz}} \right)^{0.5}\]

and the azimuthal angle is \(\varphi_{se} = 2 \pi R_2\), where \(R_2\) is a random number uniformly distributed between 0 and 1.

The Visual Setup will automatically use this ProductGenerator for an ionization interaction if an electron species is included in the reactants.

Any RxnProcess Block block which points to a productGenerator of kind = electonIonization should have the Reactants and Products in the order

reactants = [Atom Electron]
products = [Ion Electron secElectron]

electronIonization Attributes

ionizationEnergy (float, optional)

The ionization energy, in eV, of the neutral species. By default, the value of this parameter is taken from the species block of the first reactant in the RxnProcess block.

randomSeed (int, optional, default: random int)

Manually set a random seed used to determine the final velocities of the product particles.

The default is to choose a random seed at run time. To produce identical simulations, advanced users may want to manually set a seed. It is recommended not to include this parameter so that a different random number will be generated for each run.

Example electronIonization Block

<RxnProductGenerator productGenerator>
  kind = electronIonization
  #ionizationEnergy = 1.47
  #randomSeed = 789
</RxnProductGenerator>