Environmental Engineering Reference
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4.4.4
Conversion of Ions During Drift in an Electric Field
Usually different types of ions may exist in a gas when ions drift in an external
electric field. Hence, in the course of ion drift, transitions between different types
of ions are possible, and because the mobilities are different for different types of
ions, these transitions influence the time taken by ions to travel a given distance,
in particular, for their motion in a drift or gas discharge chamber. We first con-
sider this problem for inert gases, where along with atomic ions A C molecular
ions A 2 may also be present. Figure 4.10 shows the dependence on the reduced
electric field strength for the mobility of helium ions moving in helium [68], and
Figure 4.11 compares the mobilities of atomic and molecular ions in argon [21].
The number of types of ions in the molecular case may be higher. As examples,
Figure 4.10 The mobility of atomic and molecular helium ions in helium as a function of the
reduced electric field strength [68].
Figure 4.11 The mobility of atomic and molecular argon ions in argon [21].
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