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Calculation of total ionization cross section

  1. Mar 24, 2015 #1
    Hai all,
    I need some help in understanding the calculation of total ionization cross section. As per the literatures, for a gas capable of multiple ionization, the total cross section is a charge-weighted sum of partial ionization cross sections. To be more elaborate, consider the case of Xenon. Upon electron impact, Xe can become Xe+ or Xe2+ or Xe3+ ..... , cross sections of which are respectively represented as σ1, σ2, σ3 .... etc.
    Then total ionization cross section for Xe will be calculated as
    σtotal = σ1+ (2*σ2) +(3*σ3)+....... .
    So my question is, why can't we just add the partial ionization cross section to calculate total ionization cross section instead of adding charge weighted sum ?
     
  2. jcsd
  3. Mar 24, 2015 #2

    mfb

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    Staff: Mentor

    Do you want to calculate how many xenon atoms get ionized (independent of their state), or how many electrons get set free?
    Also, Xe3+ can capture electrons from other xenon atoms afterwards, leading to 3 Xe+ ions for example.
     
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