Newsgroups: sci.physics.plasma
From news@newsstand.cit.cornell.edu Wed Feb 1 16:26:48 1995
From: rilee@astrosun.tn.cornell.edu (Michael L. Rilee)
Organization: Laboratory for Plasma Studies, Cornell University
Subject: Re: onset of plasma effects

>From: ggraef@alpha1.csd.uwm.edu (Gerald Luther Graef)
>Suppose we could fill a box with ionized hydrogen. Should we expect
>to see plasma effects at room temperature?

You did not mention the density. If your ionized hydrogen is at room
pressure, then don't blink, or you'll miss the flash as the plasma
recombines. At lower densities the collision rate will drop, and the
plasma will not become a neutral gas so rapidly.

In equilibrium, in order to get, say, 50% of the hydrogen to stay ionized
(on average), you'd need some fantastically small density.

Check out Chen's 'Plasma Physics and Controlled Fusion' [1], page one, and
work with the Saha equation yourself. The Saha equation (aka law of
mass action, I believe) gives the fraction of the reactants in
equilibrium--ah--it tells you the amount of ionization expected at
equilibrium, given the plasma temperature, and density. The strongest
factor is, of course, the Boltzmann factor exp(-binding_energy/KT).

Any intro book on plasma physics (or statistical physics) will discuss
this.

Mike

[1] F.F. Chen, 1988, 'Plasma Physics and Controlled Fusion', Plenum Press, NY,
p. 1
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