Why Study Electron-Atom Collisions?

 


 
 
  Why study electron-atom collision process? Because electron-atom collisions occur so often, in so many important processes, in so many different fields of study. Consider the following factoids:
  • Electron-atom collisions play an important role is the following man-made plasmas:
    • Helium-Neon Laser
    • other gas-discharge lasers (N2, Argon-Ion, excimer, etc...)
    • semiconductor processing plasmas
    • fluorescent lamps
    • fusion plasmas
    • triboluminescence glow from crushed Lifesaver candies1

  • Electron-atom collisions also play a role in understanding the following natural phenomena:
    • primordial (Big-Bang) helium abundance
    • planetary nebula
    • other astrophysical plasmas
    • upper atmosphere dynamics

  • Frequency of electron-atom collisions on planet earth2:
    • in the ionosphere            ~1035 s-1
    • in Hg & Na street lamps ~1034 s-1
    • in fluorescent lamps        ~1031 s-1

We do not study any of these phenomena directly; instead, we study the basic collision processes:

An electron, with a fixed kinetic energy, collides with an atom (or molecule) and transfers some energy to it (via excitation, ionization). We measure the cross section (the probability) that the atom is excited to a particular state.

Thus we generate the basic science values needed to understand plasmas in numerous applied fields of study.

references
1. Jearl Walker, Scientific American (July, 1982) p. 146.

2. John F. Waymouth, "Collision Phenomena in Electrical Discharge Lamps" in Applied Atomic Collision Physics 5 Academic Press: New York (1982) p.331.
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last updated: Jan-12-1998