Geoscience Reference
In-Depth Information
Fig. 1.14
Qualitative
illustration of the Rydberg
atom-atom collision
according to
E
.Fermi
1.8.1
Symmetrical Collisions
The following data from review papers (Gnedin et al.
2009
;Smirnov
1981
)and
results in the chemo-ionization of Rydberg atoms of alkali metals obtained by
Nielsen and Dahler (
1979
) and by Huennekens and Gallagher (
1983
) will be used.
The effectiveness of the chemo-ionization in the thermal (
E
> 10
2
K) and the
subthermal (
E
< 10
2
K) ranges of the symmetrical Rydberg atom collisions was
investigated. The atom motion dynamics is not described classically in the case of
the ultracold collisions (
E
< 10
3
K). The rate constants of the chemoionization
in the thermal and subthermal regimes can be calculated in the semiclassical
approximation. In these papers, laser excitation of
n
2
Sand
n
2
D Rydberg states of
the sodium atom is carried out with the help of two pulsed tunable lasers with the
repetition rate 50 kHz.
A signal corresponding to the AI channel is measured in most of the beam
experiments. At the same time, these theoretical calculations include information
about two possible AI and PI ionization channels. We should take into account,
comparing the experimental data and the theory, that the resulting signal in the cross-
beam conditions (cross-beam conditions, CB) and the calculated rate constant kAI
correspond to both the signal caused by particle collisions of different beams and
the particle collisions within one beam (single-beam conditions, SB). It is known
that the different values of relative velocities of the partner particles correspond
to CB and SB conditions (Klyucharev and Vujnovic
1990
). The experimental data
obtained without regard to the latter circumstance can be considered as the upper
values of the CB constants:
k
tot
AI
D
k
CB
AI
C
k
S
AI
:
(1.67)
Attention was drawn to this fact only very recently. The comparison of the
experimental and theoretical data of the AI constants for intersecting beams, taking
into account the collision contribution of one beam (Eq.
1.67
) for the excited
2
Sand
2
D sodium atoms (Beterov et al.
2005
), is represented in Fig.
1.15
. The data of the
