Chemistry Reference
In-Depth Information
U
E
= E
∙ d
E
E
Cathode
Anode
hv
e
-
γ
α
A
+
dz
0
z
d
E
FIGURE 3.32
Charge carrier production in the discharge gap due to α and γ processes.
necessary kinetic energy for ionization.
exp
−
.
n
e
(
)
n
eo
=
z
z
ion
λ
ion
P
ion
=
(3.264)
This equation gives the probability that an electron has an ionization length greater
than
z
ion
.
The first Townsend coefficient α, which means the number of ionizing electron
collisions per length unit, can be achieved after division of (3.264) by λ
ion
.
Then, we replace
z
ion
and λ
ion
in
exp
−
1
λ
ion
z
ion
λ
ion
α
=
(3.265)
by use of the electron energy gain in the electric field over
z
ion
ε
ion
=
e
·
E
·
z
ion
(3.266)
and the pressure depending mean ionization path length
p
k
B
·
v
e
λ
ion
·
n
gas
=
λ
ion
·
T
gas
=
v
e
=
C
ion
(3.267)
σ
ion
·
