Environmental Engineering Reference
In-Depth Information
where the numerical factor const is of the order of 1. The same dependence of the
rate constant for this process on the problem parameters follows from the Thom-
son theory (2.68) for three body processes. Table 2.12 contains the values of the
rate constant for process (2.88) at room temperature and the values of the numeri-
cal factor in (2.89) that provide the experimental values of this rate constant.
In this consideration, we consider the process of conversion of atomic ions into
molecular ones in three body collisions as a result of interaction of three colliding
particles within the framework of one potential energy surface. But there are sever-
al electron states in the case of identical ions and atoms, and they include the even
and odd states with respect to interaction of the ion with each atom. In other words,
along with the ion-atom polarization interaction, the ion-atom exchange interac-
tion may be of importance for this process. This is demonstrated in Figure 2.21,
where the rate constant for the process
He
2
C
He
C
C
2He
!
He
is given at room temperature of atoms and a varied ion energy that depends on
an external electric field [129]. Note that in the case of the ion-atom polarization
interaction, the rate constant decreases with increasing ion energy, and the exper-
Ta b l e 2 . 12
The experimental rate constants for the three body process in (2.88) at room temper-
ature and their comparison with (2.89) [27].
A
He
Ne
Ar
Kr
Xe
,
a
0
α
1.38
2.68
11.1
16.7
27.4
K
,10
32
cm
6
/s
11
6
3
2.3
3.6
const
37
20
2.4
1.6
1.7
Figure 2.21
The three body rate constant for conversion of atomic helium into the molecular
ion (He
C
C
2He
!
He
2
C
He) at room temperature as a function of the ion energy [129].
