Environmental Engineering Reference
In-Depth Information
where
R
0
/2 is the cross section of this process for straight trajectories of a collid-
ing ion and atom. Combining these limiting cases, we conveniently represent the
cross section of resonant charge exchange in the form [65]
π
<
:
2
R
0
C
4
α
e
2
ε
α
e
2
2
R
0
,
R
0
ε
q
α
e
2
2
σ
D
res
ε
α
e
2
2
R
0
π
,
ε
where
R
0
corresponds to straight ion and atom trajectories. As is seen, in (2.46) the
cross section depends on the parameter
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
D
α
σ
2
e
2
2
R
0
ε
D
U
(
R
0
)
ε
c
x
D
,
(2.47)
4
σ
res
where
c
is the cross section of ion capture at the polarization ion-atom interac-
tion. Values of
x
for a collision energy of 0.1 eV in the laboratory frame of refer-
ence are given in Table 2.6. As is seen, although the cross section of elastic ion-
atom scattering is comparable to the cross section of resonant charge exchange
at thermal energies, elastic scattering has a weak influence on the cross section
of resonant charge exchange at thermal energies. Note that the accuracy of the
cross sections for the resonant charge exchange process evaluated on the basis of
the asymptotic theory for subthermal ion energies is better than 10%. As an ex-
ample, in Figure 2.10 the cross sections of resonant charge exchange for krypton
which were obtained on the basis of the asymptotic theory [57-59] and measure-
ments [66-74] are compared.
σ
Figure 2.10
The cross sections of resonant charge exchange for krypton. 1 - asymptotic formu-
la, experiment: 2 - [70], 3 - [71], 4 - [68], 5 - [69], 6 - [72], 7 - [66, 67], 8 - [73], 9 - [74].
