Environmental Engineering Reference
In-Depth Information
The above formulas for the ion drift velocity in the limits of low and high elec-
tric field strengths allow one to obtain the following expression in an intermediate
range of electric field strengths: as [54, 56, 64]
r
2
T
M
0.48
w
i
D
,
(4.99)
(1
C
0.22
3/2
)
1/3
where
is the solution of the equation
eE
D
res
q
2
M
(4.5
)
(4.100)
2
TN
a
σ
C
1.6
and the cross section of resonant charge exchange depends weakly on this param-
eter
,and
Figure 4.9 shows the mobility of atomic argon ions in argon at low and medium
electric field strengths, where the mobilities according to (4.99) and (4.100) are
compared with experimental data [21, 65, 66].
Let us use the above formulas for a simple estimation, namely, let us find the
reduced electric field strength at which the average energy of the He
C
ioninhe-
lium is twice that at zero field. Because the average kinetic energy in directions
. Figure 4.8 gives the dependence of the reduced ion drift velocity on
Figure 4.8
The ion drift velocity as a function of the reduced electric field strength in the case
of the resonant charge exchange process. Dotted lines correspond to the limits of low and high
electric field strength.
Figure 4.9
The mobility of Ar
C
ions in argon. Theory: formulas (4.99) and (4.100) [54, 56, 64]
- open circles. Experiment: closed circles - [65], solid curve - [21, 66].
