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P, torr
Fig. 1.10
Dependence of the molecular ion current on the square of the resonance level concen-
of energy. Figure 1.10 shows the dependence of the IAI ion current from the cell
with cesium vapor on the square of the concentration of excited atoms produced
in the optical excitation resonant states, in the mode of the resonance radiation
transfer. The measurements were made when the cesium vapor pressure was 10 3 to
10 2 mmHg at T D 425 K. We see that the dependence IAI D f (N 2 (6 2 P)) is linear in
the entire range of the vapor pressure. Similar associations were observed for other
alkali atoms (Rb, Na, K). The temperature dependence of the chemo-ionization rate
constants shows that this process has a threshold with the corresponding value of
the activation energy E .
A model representation of the unsplit covalent potential curve is valid for the
quasi-molecule states formed from the atoms in the 2 S state. In fact, 24 of the
intermediate quasi-molecule states correlated at R !1 with two n 2 P excited alkali
atom states are involved in the reactions (1.58) and (1.59). The model used assumes
that the resulting values describe one effective potential curve instead of the beam
real terms.
There are few theoretical studies of AI processes involving the resonantly excited
heavy alkali atoms in the literature. The expression for the constant k ( T )ofthe
endothermic process for cesium and rubidium atoms, with taking into account the
twist effect, was obtained by Klyucharev and Vujnovic ( 1990 )(Table 1.4 ).
Devdariani ( 1979 ), based on the experiment to pair collisions of atoms 2Cs(6 2 P)
and 2Rb(5 2 P), and using the semiclassical approximation to the Maxwellian atomic
velocity distribution in the thermal energy range, described the constant process of
Eq. 1.58 by the expression
k i .T/ D V c R c .T/exp . U 0 .R c /=T/
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