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The role of the inversion population in barium cloud ionization in the upper atmosphere
Atmospheric und Terrestrial
Journal of Printed in Great
Physics, Vol.
55, No.
1, pp. 123-124,
1993
0021-9169/93 55.00+ .Bll Pergamon Press Ltd
Bntain.
BRIEF REPORT The role of the inversion population in barium cloud ionization in the upper atmosphere E. I. GOLBRAIKH* and S. SH. NIKOLAISHVILI Institute of Applied Geophysics, Moscow. 129128, Russia (Received injnalform
1 June 1992)
28 August 1991; accepted
Abstract-The influence of the population of barium atoms on barium cloud ionization in the upper atmosphere is investigated. It is shown that the experimental values of the effective time for barium cloud ionization
is determined
by the metastable
3D states’ inversion
population.
One of the problems of modelling the barium cloud (BC) luminosity, dynamics and kinetics in the upper atmosphere (UA) is a discrepancy between the experimental (Q) and theoretical (7,) values of the ionization time constant. Experimental values of z0 are z 15-35 s (HALLINAN, 1988; RIEGER et al., 1970), and the theoretical Z, is z 50-70 s (DRAPATZ, 1972 ; GOLBRAIKH et al., 1990). The aim of our work is to investigate the influence of the initial BaI population (going out of the injector) on BC ionization in the UA. Optically thin BC spectroscopy in the UA is considered by GOLBRAIKH et al. (1990). A Boltzmann distribution was taken in this work for the BaI initial population, and it was found that, for an optically thin BC that was sunlit, the value t, z 66 s. However, usually artificial barium clouds are generated by chemical reactions of considerable energy. Because of this, the metal barium part turns into a vapour (ROSENBERGand BEST, 1971) and its initial population can differ from the Boltzmann distribution. The main method of barium ionization by sunlight is ionization from the metastable states, ‘D and 3D, the energies of which are 1.4 and 1.1 eV, respectively. It follows from this that metastable levels can be populated in the metal barium evaporation process. Calculation of the BC shows that the anomalous initial ‘D level population does not lead to much of a change of T, value. This result is due to the metastable ‘D resonant ‘pumping over’ to the ground state (‘S) through higher levels. As the 3D state does not have channel for this ‘pumping over’, the transition time to the ground state is therefore much more than the
ionization time from this state. In this way, the initial 3D metastable level population is the main influence on the speed of BC ionization. The dependence of z, on the initial population, y = N(3D)/N, (where NOD) is the concentration of barium atoms in the 3D state; N, is the total concentration in BC) is computed and is shown in Fig. 1. A value of T,, = 15-35 s found in experiments conforms to an initial population width y x 0.65-0.8 ; therefore, barium atoms can have an inversion population (to state ‘D) when leaving the injector.
* Permanent address : Physics Department, Ben-Gurion University of the Negev, Beer-Sheva 84100, Israel.
Fig. 1. The effective time constant for ionization of a barium cloud. The experimental values conform to y N 0.65-0.8.
70 60 3 .g
: ._ ti Q 5
50 40 30
0
0.2
0.4
0.6
0.6
1.0
Y
E. I. GOLBRAIKH and S. SH. NIKOLAISHVLI
124 Indirectly, firmed
our calculations
by the results
BEST (1971).
of the y value are con-
of the work of ROSENBERG and
It was shown
here that the anomalous
intensity
in the
observed
in the first 5 s after the injection.
osity conforms
wavelength
to the resonant
region
z 611 nm
transition
was
3D and the 3P state. If the population occurs in accordance luminosity experimental
between
method
the
in the region
In this way, perhaps,
This lumin-
data
of barium atoms
with the Boltzmann
distribution,
x 611 nm has small intensity. the Q values
are
closely
determined
connected
with
from the
of BC formation.
REFERENCES DRAPATZ S. W.
1972
GOLBRAIKHE. I., KOSAREVN. I., NICOLAISHVILYSH. S. and SHKEDOV I. M
1990
HALLINANT. G.
1988
RIEGERE., NEUSSH., LUTSR., MEYERB., HASERL., LODE H., STOCKER J. and HAERENDEL G. ROSENBERG N. W. and BE_ST G. T.
1970
1971
The radiative transfer problem
in freely expanding gaseous clouds and its application to barium cloud experiments. Planel. Space Sci. 20,663. Ionization of optically thin barium cloud. Geomagn. Aeron. 30, 350. Observed rate of ionization in space-charge release of barium in the ionosphere. J. geophys. Res. 93,8705. High altitude releases of barium vapour using a rocket. Ann. Geophys. 26,845. Chemistry of barium released at high altitudes. J. them. Phys. 75, 1417.
Journal of Printed in Great
Physics, Vol.
55, No.
1, pp. 123-124,
1993
0021-9169/93 55.00+ .Bll Pergamon Press Ltd
Bntain.
BRIEF REPORT The role of the inversion population in barium cloud ionization in the upper atmosphere E. I. GOLBRAIKH* and S. SH. NIKOLAISHVILI Institute of Applied Geophysics, Moscow. 129128, Russia (Received injnalform
1 June 1992)
28 August 1991; accepted
Abstract-The influence of the population of barium atoms on barium cloud ionization in the upper atmosphere is investigated. It is shown that the experimental values of the effective time for barium cloud ionization
is determined
by the metastable
3D states’ inversion
population.
One of the problems of modelling the barium cloud (BC) luminosity, dynamics and kinetics in the upper atmosphere (UA) is a discrepancy between the experimental (Q) and theoretical (7,) values of the ionization time constant. Experimental values of z0 are z 15-35 s (HALLINAN, 1988; RIEGER et al., 1970), and the theoretical Z, is z 50-70 s (DRAPATZ, 1972 ; GOLBRAIKH et al., 1990). The aim of our work is to investigate the influence of the initial BaI population (going out of the injector) on BC ionization in the UA. Optically thin BC spectroscopy in the UA is considered by GOLBRAIKH et al. (1990). A Boltzmann distribution was taken in this work for the BaI initial population, and it was found that, for an optically thin BC that was sunlit, the value t, z 66 s. However, usually artificial barium clouds are generated by chemical reactions of considerable energy. Because of this, the metal barium part turns into a vapour (ROSENBERGand BEST, 1971) and its initial population can differ from the Boltzmann distribution. The main method of barium ionization by sunlight is ionization from the metastable states, ‘D and 3D, the energies of which are 1.4 and 1.1 eV, respectively. It follows from this that metastable levels can be populated in the metal barium evaporation process. Calculation of the BC shows that the anomalous initial ‘D level population does not lead to much of a change of T, value. This result is due to the metastable ‘D resonant ‘pumping over’ to the ground state (‘S) through higher levels. As the 3D state does not have channel for this ‘pumping over’, the transition time to the ground state is therefore much more than the
ionization time from this state. In this way, the initial 3D metastable level population is the main influence on the speed of BC ionization. The dependence of z, on the initial population, y = N(3D)/N, (where NOD) is the concentration of barium atoms in the 3D state; N, is the total concentration in BC) is computed and is shown in Fig. 1. A value of T,, = 15-35 s found in experiments conforms to an initial population width y x 0.65-0.8 ; therefore, barium atoms can have an inversion population (to state ‘D) when leaving the injector.
* Permanent address : Physics Department, Ben-Gurion University of the Negev, Beer-Sheva 84100, Israel.
Fig. 1. The effective time constant for ionization of a barium cloud. The experimental values conform to y N 0.65-0.8.
70 60 3 .g
: ._ ti Q 5
50 40 30
0
0.2
0.4
0.6
0.6
1.0
Y
E. I. GOLBRAIKH and S. SH. NIKOLAISHVLI
124 Indirectly, firmed
our calculations
by the results
BEST (1971).
of the y value are con-
of the work of ROSENBERG and
It was shown
here that the anomalous
intensity
in the
observed
in the first 5 s after the injection.
osity conforms
wavelength
to the resonant
region
z 611 nm
transition
was
3D and the 3P state. If the population occurs in accordance luminosity experimental
between
method
the
in the region
In this way, perhaps,
This lumin-
data
of barium atoms
with the Boltzmann
distribution,
x 611 nm has small intensity. the Q values
are
closely
determined
connected
with
from the
of BC formation.
REFERENCES DRAPATZ S. W.
1972
GOLBRAIKHE. I., KOSAREVN. I., NICOLAISHVILYSH. S. and SHKEDOV I. M
1990
HALLINANT. G.
1988
RIEGERE., NEUSSH., LUTSR., MEYERB., HASERL., LODE H., STOCKER J. and HAERENDEL G. ROSENBERG N. W. and BE_ST G. T.
1970
1971
The radiative transfer problem
in freely expanding gaseous clouds and its application to barium cloud experiments. Planel. Space Sci. 20,663. Ionization of optically thin barium cloud. Geomagn. Aeron. 30, 350. Observed rate of ionization in space-charge release of barium in the ionosphere. J. geophys. Res. 93,8705. High altitude releases of barium vapour using a rocket. Ann. Geophys. 26,845. Chemistry of barium released at high altitudes. J. them. Phys. 75, 1417.