Environmental Engineering Reference
In-Depth Information
Figure 2.19 The cross section of electron attachment to the oxygen molecule as a function of
the electron energy at different gas temperatures [123].
zero electron energy. We give in Table 2.11 the rate constants for electron attach-
ment to halomethane molecules at room temperature. As is seen, the rate constant
for this process is nonzero at low electron energies, although the position of the
autodetachment level for electron capture depends on the type of molecule. The
rate constants for electron attachment differ by an order of magnitude for different
halomethane molecules which have identical structure.
The electron attachment process is of importance for electric breakdown of gases
or for gas discharge. A small concentration of electronegative molecules may give
an effective loss of electrons in a gas discharge plasma as a result of electron attach-
Ta b l e 2 . 11 The rate constants for electron attachment to halomethane molecules at room tem-
perature [125, 126].
Rate constant, cm 3 /s Molecule
Rate constant, cm 3 /s
Molecule
10 15
10 9
CH 3 Cl
<
2
CF 2 Cl 2
1.6
10 12
10 7
CH 2 Cl 2
5
CFCl 3
1.9
10 9
10 8
CHCl 3
4
CF 3 Br
1.4
10 12
10 7
CHFCl 2
4
CF 2 Br 2
2.6
10 12
10 9
CH 3 Br
7
CFBr 3
5
10 8
10 7
CH 2 Br 2
6
CF 3 I
1.9
10 7
10 7
CH 3 I
1
CCl 4
3.5
10 16
10 8
CF 4
<
1
CCl 3 Br
6
10 13
CF 3 Cl
1
 
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