Geoscience Reference
In-Depth Information
A
100
75
N
0
=1,5
.
10
13
cm
-3
2,0
.
10
13
3,5
.
10
13
5.0
.
10
13
6,5
.
10
13
16
.
10
13
50
25
N
2
,10
18
cm
-6
0
25
50
75
100
125
Fig. 1.11
Experimental energy spectrum of electrons with energy from 0 to 2.1 eV formed during
resonance excitation of sodium atoms
Fig. 1.12
Relative
populations of the vibrational
states of the molecular ion
Na
2
C
in the vicinity of the
first peak in Fig.
1.12
,
obtained by electronic
high-resolution spectroscopy
(Blang´eetal.
1997
)
same time, the main contribution, which leads to a difference in the measured AI
constants in both cases, may be caused by the marked difference in the collision
energy threshold for the ionization (Klyucharev and Vujnovic
1990
).
Electron spectroscopy methods enable receiving reliable information not only
about the different ionization processes, but also about the second kind of collisions
of excited atoms with electrons. Figures
1.11
and
1.12
show an overview spectrum
of the electrons, which can be registered for selective excitation of the 3
2
P state of
the sodium atoms. The first maximum of the electron energy distribution close to
zero energy corresponds to the AI process. The maximum at
E
D
2.1 eV is caused
by the heating of slow electrons produced by the photo-ionization during collisions
of the second kind with excited 3
2
P atoms. Along with the second kind of collisions
of Na
C
e
!
Na
C
e
, we can observe the processes of the triple collisions
Na
C
Na
C
e
!
2Na
C
e
; they correspond to the maximum of the electron
spectrum at
E
D
4.2 eV.
