chemical physics of discharges - Argonne National Laboratory

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I
I
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To find (t2)av, we assume that collisions are random events and the collision
frequency is independent of speed. We can then write that the probability of a
collision occurring in the interval t to t + dt following the precdding collision is
. .
for which the average value of t2 is 2@ where< = 112 is the mean collision time.
Eq. (11) then becomes
a&#
t2.
= ma-t
If we also average over all speeds of electrons and neglect some of the finer pohts
of statistics, Eq. (13) becomes
where A is the mean free path and c is the mean speed of the electrons.
This quantity, in the steady state, will equal the right hand side of Eq. (7)
averaged over all electrons. If we let d.ls 1 -2 c
2
Thus we would expect that the mean speed would be given by
-
and the mean energy of the electrons in the steady state by
(13)