JPRS ID: 9856 USSR REPORT PHYSICS AND MATHEMATICS

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• Sequence Number: 37
• Content Type: REPORTS

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JPRS L/9856
~ 20 July 1981
~ l1 SS R Re ort
p
PHYSICS AND MATHEMATICS
(FOUO 7/81)
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~7PRS L/9856
20 July 1981
USSR REPORT
PHYSICS AND MATHEMATICS
(FOUO 7/81)
CONTE~ITS
CRYSTAIS AND SII~CONDUCTORS
Current Problems in E1lipsometry 1
FLUI~ DYN~CS
Propagat�ion of a Slow Luminous Air Combustion Wave in a
Neodymium Laser Beam 4
LASERS AND MASERS
Optical Cavities and the Problem of I}ivergence of Zaser I.
~+T111SS1OT1 14
CW Emission of an Iodine Photodissociation Zaser ~5
Investigation of Thermal Self-Stress of a Li.ght Pulse in a
Tur�bulent Medium by a Method of Statistical Tests ~ 33
Electric-Discharge Chemical HF-Laser With High Pulse Recurrence
Rate 39
- OPTICS AND SPECTROSCOPY
Applied Physical Optics ~3
Narrow-Band Tunable Qptical P`i.lter Based on A CdGa2S4 Single
Crystal 1~8
- a- [ III - USSR - 21.H S&T FOUO)
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PLASMA PHYSICS
Plasma Physics, Physics of Electronic and Atomic Collisions,
Physical Gas Dynamics 51
THERMODYNAMICS
Heat Conductian and Convective Heat Exchange 55
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CRYSTAIS AND SII~IICONDUCTORS
UDC 535.51
CURRENT PROBLEMS IN ELLIPSOMETRY
Novosibirsk SOVREMENNYYE PROBLEMY ELLIPSOMETRII in Russian 1980 (signed to press
10 Nov 80) pp 2-3, 185-186
[Annotation,editor's preface and table of contents from book "Current Problems
in Ellipsometry", edited by Anatoliy Vasil'yevich Rzhanov, Institute of Physics
of Semiconductors, Siberian Department, USSR Academy of Sciences, Izdatel'stvo
"Nauka", 1400 copies, 186 pages]
[Text] This collection is devoted to research dealing with the main areas of devel-
opment of ellipsometry and its applications. The papers examine an extensive class
of problems in this promising field of science--from the theoretical aspects of
the reflection of light to the development of various types of ellipsometers de-
signed for the practical requirements of semiconductor microelectronics.
Intended for experimental physicists and technological engineers working in the
field of physical electronics, surface physics and chemistry and the physics of
semiconductors.
rrom the Editor
According to convention established over the last 10-15 years, the term "~ll.ipsom-
etry" denotes an optical technique of studying the state of a surface and determin-
ing (measuring) the parameters of thin films based on analysis of the change in
state of polarization of a light beam upon reflection.
There are two factors that make ellipsometric measurements particularly attractive.
In the first place, they are not only non-contact and non-destructive, but also
"non-disturbing" to the investigated system under condition that the wavelength
and intensity of the light are properly selected. This feature enables ellipso-
metric measurements directly in the course of the given process, high temperature
of the surface of the specimen and aggressiveness of the ambient medium being no ~
problem.
In the second place, the state of polarization of the reflected light is quite
sensitive to mini.mum changes of surface state and parameters of thin-film systems.
For example the best ellipsometers can fix changes in the adsorption coating of
a surface of the order of thousandths of a monolayer.
1
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Since processes on phase interfaces and in thin-film systems are becoming a research
topic in many fields of natural science and technolgy (in the physics and physical
chemistry of surfaces, microelectronics, science of materials and metallurgy, optics
and mechanics, biology and medicine, atomic and genetic engineering), it is under-
standable why there has l~een a recent upsurge of interest in el'lipsometry with
its unusual capabilities.
The First All-Union Conference on Ellipsometry as a Method of Studying Physico-
chemical Processes on the Surface of Solids was held in June of 1977 at Akadem-
gorodok in the Novosibirsk Science Center of the Siberian Department of the USSR
Academy of Sciences. This collection contains the most interesting papers delivered
at that conference.
Contents page
_ From the Editor 3
A. V. Rzhanov, "Ellipsometry--an effective method of studying the surface of
solids and thin films" 4
Yu. A. Kontsevoy, "Ellipsometric methods.~.f inspection in microe~._.ectronics" 11
_ T. N. Krylova, "Using Ellipsometry to study thin films on a glass surface" 19
M. A. Krykin, S. F. Timashev, "Theoretical aspects of optical methods of
studying *ransition layers on an interface" 26
V. A. Antonov, V. I. Pshenitsyn, "Reflection of light in the presence of a
thin conductive layer" 29
V. A. Shepelin, E. V. Kasatkin, "Technical characteristics of ellipsometers" 37
V. A. Shepelin, F. Ya. Frolov, A. P. Kuzyayev, Ye. V. Nikitin, B. K. Sokolov,
"Spectral ellipsometer for physicochemical research" 42
Ye. N. Kudryavtsev, i.. R. Rezvyy, M. S. Finarev, Yu. A. Kontsevoy, V. N. Vlasov,
"Ellipsometer on wavelength of 10.6 um and its use" 45
A. V. Arkhipenko, Yu. A. Blyumkina, "Modulation null-ellipsometry: analysis
and optimization of modulation frequency selection" 56
- Yu. I. Uryvskiy, K. A. Lavrent'yev, A. N. Sedov, A. A. Churikov, V. A. Fopov,
I. R. Vinnikov, "Facility for studying physicochemical processes of
growth and and etching of dielectric films on the surface of solids
with an automatic ellipsometer built into the working chamber" 71
Yu. I. Uryvskiy, K. A. Lavrent'yev, A. N. Sedov, V. A. Popov, V. S. Ivanov,
N. A. Latysheva, "Investigation of the kinetics of anodizing silicon
plates in a plasma with the use of an automatic ellipsometer" 78
V. A. Tyagay, Yu. M. Shirshov, N. A. Rastrenenko, "Measurement of optical
constants of a semiconductor-dielectric system by the method of
ellipsometry with immersion" 81
B. M. Ayupov, N. P. Sysoyeva, "Some examples of using immersion liquids in
ellipsometry" $8
E. V. Kasatkin, "Methods of calculating multilayer films from results of
ellipsometric measurements, and computer programs" 94
V. V. Batavin, N. M. Zudkov, R. N. Kochin, "A method of ellipsometric inspec-
tion of two-layer dielectrics using inverted nomograms" 97
I. M. Minkav, V. V. Veremey, "The matrix method in ellipsometric calculations" 99
A. A. Belinska, R. P. Kaltynya, I. A. Feltyn', I. E. Eglitis, I. A. Eymanis,
"Ellipsometric investigation of the surface of silicon treated in a
high-frequency gas-discharge plasma" 107
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0. I. Artamonov, S. A. Komolov, Ye. G. Molochnova, I. I. Yakovlev, "Ellipso-
metric study of the surface of Mo (111) with vacuum heat treatment" 110
V. V. Batavin, N. M. Zudkov, R. N. Kochin, "Ellipsometric inspection of a
silicon polycrystal - silicon dioxide - silicon single crystal structure�1 114
M. S. Finarev, R. R. Rezvyy, "Checking the thickness and properties of films
of polycrystal silicon by using ellipsometry" 116
P. A. Bakhtin, A. V. Yemel'yanov, "Investigation of self-oxides on AIIIBIV
semiconductors by methods of ellipsomeCry and Auger spectroscopy" 122
V. N. Antonyuk, N. D. Dmitruk, I. P. Lisovskiy, 0. I. Mayeva, "Ellipsometric
study of dielectric-semiconductor systems by an in situ method and on
_ etching wedges" 127
_ V. Ye. Drozd, S. I. I~.ol'tsov, T. A. Redrova, "Investigation of condensation
. reactions on the surfa~e of semiconductors (reactions of molecular
layering) by using ellipsometry" 134
G. V. Sveshnikova, S. I. Kol'tsov, V. B. Aleksovskiy, "Investigation of
multilayered systems on the surface of s3licon by the method of
ellipsometry" 141
; V. A. Tyagay, 0, V. Snitko, N. A. Rastrenenko, V. V. Milenin, V. I. Poludin,
V. Ye. Pri~nachenko, "Ellipsometric study of a silver-doped silicon
surface" 145
A. G. Grivtsov, R. M. Yergunova, Z. M. Zorin, M. A. Krykin, Yu. N. Mikhaylov-
skiy, A. A. Necha}~ev, S. F. Timashev, A. Ye. Chalykh, "Ellipsometr3c
investigation of the initial stages of deposition of inetals on dielec-
tric substrates" 154
Z. I. Kudryavtseva, V. A. Openkin, N. A. Zhuchkova, Ye. I. Khrushcheva,
N. A. Shumilova, "Ellipsometric study of oxide films on metals" 158
A. P. Garshin, G. V. Sveshnikova, V. B. Aleksovskiy, "Ellipsometry in
studying the process of chemical modification of silicon carbide" 162
N. Yu. Lyzlov, V. I. Pshenitsyn, I. A. Aguf, "Ellipsometric study of the
behavior of a lead sulfate electrode in the presence of ~ome surfactants" 166
I. I. Ushakov, S. I. Kol'tsov, V. K. Gromov, "Capabilities for using pulsed
magnetic fields in ellipsometric facilities" 172
V. N. Morozov, "Theoretical investigation of the possibilities of ellipso-
metric methods in ATR spectroscopy" 176
A. I. Pen'kovskiy, "Ellipsometric measurements in the A.TR technique" 179
COPYRIGHT: Izdatel'stvo "Nauka", 1980. -
6610
CSO: 1862/183
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FLUID DYNAMICS
UDC 533.9.15+537.52.7
PROPAGATION OF A SLOW LUMINOUS AIR COMBUSTION WAVE IN A NEODYMIUM LASER BEAM
P4oscow KVANTOVAYA ELEKTRONIKA in Russian Vol 8, No 4(106), Apr 81 pp 751-759
[Article by I. A. Bufetnv, A. M. Pr.okhorov, V. B. Fedorov and V. K. Fomin, Physics
Institute imeni P. N. Lebedev, USSR Academy of Sciences, Moscow]
[Text] An investigation is made of large-sca~.e propagation and
maintenance of an optically thin laser plasma of atmospheric
air in the slow combustion mode on a length of up to 20 cm for
a duration of ~5 ms by means of a neodymium laser with emission
energy of 8 kJ. An optical discharge is achieved for the first
time in the slow combustion mode with steady-state pattern of
gas movement. A model is prop:~sed for describing the gas dynam-
. ics of discharge propagation in which the ratio of the observed
velocity to the velocity of movement of the discharge through a
quiescent gas is equ~i to the ratio of velocit~es of sound in the
discharge and in a cool gas. Measurements are made of the veloci-
_ ties of wavefront propagation and the coefficient of absorption
of the discharge plasma. Thresholds of induced initiation and
propagation of a luminous air combustion wave are determined.
1. Introduction
Slow combustion of an optical discharge in a laser beam was discovered in 1969.
Experiments of Ref.l done in atmospheric ai.r demonstrated induced initiation, sub-
sonic propagation and prolonged maintenance of an optical discharge plasma by the
emission of a neodymium laser operating in the free lasing mode. Initiation of
the discharge at a laser radiation intensity much lower than the optical break-
down threshold was achieved by inoculating the laser beam with an absorbing plasma
produced by an auxiliary electric discharge. After discharge ignition by laser
radiation absorption, the plasma propagated forward and back along the laser beam
at subsonic velocity, filling the caustic surface of the focusing lens symmetrical-
ly relative to the initiation point. The optical thickness of the plasma on a
wavelength of 1.06 um was small. Discharge plasma propagation in the laser beam
was interpreted, as in slow chemical combustion, on the basis of a thermal conduc-
tivity mechanism of energy transfer. In calculating the observed velocity of dis-
charge propagation, consideration was taken of th~ expansion of gas in the com-
bustion front by analogy with chemical combustion from the closed end of a tube.
~
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It should be noted that the use of an inoculating plasma for induced initiation
of luminous detonation was proposed in 1968 in Ref. 11. In that same year, Ref. 12
discussed rf discharge in a gas through an induction coil as a slow combustion
process. At the same time, propagation of a microwave plasma in a waveguide that
had been described in 1961 [Ref. 13] was not interpreted on the basis of a slow
combustion mechanism until 1971 [Ref. 14] after the research of Ref. 1-3.
A distinguishing procedural feature of the experiments of Ref. 1 was the simi-
larity of the experimental situation to the simplest case from the standpoint of
theory of propagation of a weakly absorbing optical discharge in a beam with cy-
?indrical symmetry. This peculiarity is associated with the use of a powerful
laspr in Ref. 1, with a power level permitting the use of a lens with small rela-
tive apoerture for focusing. Apparently this feature was the reason that subse-
quent theoretical calculations [Ref. 2-6] were verified by the authors on the basis
of the experimental material of Ref. 1. We are referring to a uniform model of
motion of the discharge front and to calculation of the threshold conditions,
derivation of a formula for the rate of propagation of the discharge with con-
sideration of the threshold [Ref. 2-4] and also to accounting for the influence
that radiative thermal conductivity in the ultraviolet part of the spectrum of
the self-radiation of the discharge has on motion of the ionization front [Ref.
S, 6].
Our research continues the experiments of Ref. 1 with a number of important changes.
Our analysis of the data of Fig. 3 in Ref. 1 showed that the velocity of the dis-
~ charge front from time t= 0.4 ms after the onset of the laser pulse to t=1 ms de-
creases monotonically from 30 to 10 m/s. (On this time segment we can obviously
disregard the influence that gas movement caused by energy release in the initiat-
ing electric discharge has on V. Actually, according to the theory of a point
explosion [Ref. 15] the corresponding ch~rafter~stic time of attenuation of pertur-
bations caused by energy release is to= E~3p ~2p-~6 (p is density, p is pressure
of the medium, E is energy), which for atmospheric pressure and E= 100 J gives
to= 0.36 ms.) The observed velocity reduction can be attributed to two causes:
a fairly rapid drop in ti.me in the power of the radiation feeding the discharge,
and also the short dura~ion of the laser pul~e, during which the velocity of motion
of the front does not have time to reach the steady state. To obtain the sta-
tionary gasdynamic pattern of laser plasma propagation in the slow combustion mode,
we made the following corrections in the conditions of the experiment of Ref, l:
increased the laser pulse duration to 5 ms with a corresponding increase in the
energy of the laser facility; made the emission power close to constant over a
longer part of the laser pulse duration; eliminated the spike modulation that oc-
curred in Ref. 1. These experiments for the first time gave an optical discharge
in the slow combustion mode with steady-state pattern of gas movement in the dis-
charge. To describe the influence that expansion of the gas heated in the cor~-
busion front had on the observed rate of motion of the front, in addition to the
previously used model of combustion from the closed end of a tube, a model was
- proposed with a better fit to the conditions of steady-state gas dynamics of the
discharge, taking consideration of the motion of hot gas behind the combustion
front.
2. Experimental Results
Our experiments were done on a laser stand with emission parameters about an order
of magnitude higher than in the first experiments [Ref. 1].
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The main laser that maintained the discharge was a neodymium glass unit with energy
of up to 8 kJ and radiation pulse duration of 5 ms at the base. An oscillogram
of the lasing pulse is shown in Fig. 1[photo not reproduced]. The lasing pulse
was smooth. The spikeless lasing structure was achieved by using a master laser
with stable cavity close to confocal, and by minimizing the feedback between
amplif ier and laser due to scattering by the optical elements. The main laser
beam was focused by a lens with focal length of 1 m. Zhe length of the caustic
curve determined by the relation R > 0,10 ~ 34,0 3,53 5.$ 0,40(9,2)
3 5 ~ 4,3 0,05 5,5 32,0 3,76 5~9 0,33(7,6)
4 ' ~ a ~ !1 26,5 4,53 3,6 0,24(5,6)
5 a s s s 16,5 24,0 5,00 2.5 0,19(4,3)
6 y ~ D 0,10 I1 20,0 6,00 4,9 0,44(10,1)
7 10 ~ 2,9 0,05 a I5,5 7,75 2,5 0,194(4,5)
8 ~ 400 2,5 ~ r 22,0 5,47 4,1 0,194(4,5)
9 ~ 500 2,2 > > 26,0 4,63 5,3 0,187(4,3)
Notes: 1) at y= 0.1 s-1 the gas temperature was not determinecl by photo-
_ chemistry, but rather by the heating of the laser tube walls by the pump-
ing lamps to 200-300�C, depending on the conditions of air cooling; 2)
the use of values of k5 double (11�10-17 cm3/s) and triple (16.5�10-17
cm3/s) the value obtained in Ref. 8 reflects the intent to determine the
- influence of contamination of the working gas that may occur under the
operating conditions of the iodine photodissociation laser; 3) the value
of vopt was calculated for ~Z= 12 cm; 4) the gain was calculated for a
laser tube (see Fig. 2) with consider~tion of the fact that radiation is
- amplified by a factor of G~aX with 8 round trips of the optical cavity,
i. e. in accordance with the formula 10 lg (GmaX) = 4.34�8QVOptaopt [dB];
in parentheses: 100 ln (Gmax~~- 1~J0�8QVOptaopt ~~~Pass] (~800(Gmax - 1~~�
Fig. 2. Diagram of cw iodine photodisso-
6 ciation laser:
5 -
~ 1--6.5-liter bottle of working gas; 2--
, valve; 3--inlet with permanent-magnet
- regulation of gas flow; 4--illuminated
- ~ ~ � ' " sections of the l aser tube; ~---valve;
~ 4 B~ 6--liquid nitrogen trap; 7--device for
measuring the lifetime of iodine atoms
~ and gas velocity; 8--resonator mirrors;
9--valve for connection to evacuation or
g ~ 10 ~ inlet system; 10--3-liter buffer tank
3
_ ~
1
T~
The logarithm of the gain is proportional to a(~t)/(~t) (see (7)). Maximum gain
Gmax corresponds to points of tangency (~topt~ aopt~ of curves a(Ot) with straight
lines passing through the coordinate origin. From this we can readily find
ln Gmax- QOZaopt/OtoPt and vopt= ~Z/Otopt. The value of cr for the strongest hyper-
- fine component of radiation on frequency v3k (F = 3, F'= 4) was found from data
of Ref. 14.
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The table summarizes some results of calculations showing that gain sufficient
for overcoming the lasing threshold may be attained at a low gas velocity obviously
corresponding to laminar flow (Reynolds number on the order of 1000 or less) if
a laser tube is used that consists of a number of relatively short illuminated
sections (4 in Fig. 2) with ~Z~ 10-20 cm connected in parallel in the flow scheme.
3. Experiment
Continuous lasing on a wavelength of 1315 nm was observed with flow of gaseous CF3I
through a quartz tube with inside diameter of 16 mm placed between two cylindrical
low-pressure mercury vapor lamps fed from a SO Hz ac line. The lamps were devel-
oped by Yu. A. Martsinkovskiy and S. A. Yakovlev, and operate in modes close to
those descr ibed in Ref. 15 if we disregard the fact that they were designed for
supply from alternating current, as opposed to those of the Brown Boveri Company,
and therefor e they have two incandescent electrodes each. The length of the work-
ing section of the lamps is 80 cm, diameter 100 mm, working current 8?,, voltage
100 V, temp e rature of the mercury branch tube 50-70�C. A more detailed description
of the design and an investigation of the characteristics of these lamps will be
published in a separate article. The length of the illuminated part of the laser
tube was 48 cm. The gas flow branched as shown in Fig. 2 into four parts flowing
around the 1 aser tube in a path with length of ~Z= 12 cm at a velocity of 2.5 m/s.
This velocity refers to the paraxial part of the laser tube, and in view of para-
bolic radial distribution is close to the maximum. The given value of the velocity
was determined from the location of the delayed maximum on the oscillogram of at-
tenuation of luminescence of a= 1315 nm that was excited by an IFP-600 flash tube
simultaneously in two cross sections of quartz tube 7(Fig. 2) separated by a dis-
tance of 3 cm along the gas flow, and was recorded by a germanium photodiode close
to the lower (downstream) cross section of this tube. Fig. 3[photo not reproduced]
shows one of the oscillograms corresponding to the conditions of the experiment.
Diffusion of atoms of I* to the wall considerably weakens contributions to the
luminescence signal on the part of the sections of gas flow near the wall.
The ends of the laser tube are fitted with quartz windows 2.8 mm thick set at the
Brewster angle. Concave spherical mirrors (8 in Fig. 2) were used with radius
of curvature of 1 m and transmission of 0.2% on a wavelength of 1315 nm. The length
of the cavity was 140 cm. Gas fl~w arose due to the pressure differential between
the gas stor ed in bottle 1 and the gas in liquid nitrogen trap 6 that acted as
the receiver of the used working fluid. The velocity and pressure of the gas in
the laser tube could be regulated by inlet 3 with magnetic flow regulation and
by valve 5 p receding the trap. Lasing arose when valve 2 was opened after a re-
liminary 5-minute warmup of the mercury vapor lamps. At a pressure of the stored
gas of 80 kPa (0.82 atm) the lasing duration reached 83 s(Fig. 4[photo not repro-
duced]). During this time the gas pressure in the laser tube did not exceed 3 kPa.
According to our estimates, pressure increases (due to buffer tank 10) for about
10 s, after which a slow decline sets in. Fig. 4 shows a recording of the signal
of the germanium photodiode that registers the radiation passing through one of
the mirrors. It can be clearly seen that in the vicinity of maximum pressure the
laser emiss ion power falls off (t~ 13 s). At the 26-th second, the cavity close
to the other mirror was covered for 3.3 s by a glass plate oriented approximately
parallel to the plane of the Brewster window. As Fig. 4 shows, this resulted in
almost total suppression of lasing. Lasing was cut off when the pressure of the
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gas in bottle 1 fell to 15 kPa. In one of the experiments, stable cw lasing was
observed at ~Z = 10 cm.
Fig. 5[photo not reproduced) shows oscillograms of the lasing (curve 1) and pumping
_ (curve 2) signals. Pumping radiation on a= 254 nm was recorded by "sun-blind" ptioto-
cell F-7, and the laser emission was registered by a germanium photodiode. The
mercury lamps were fed in phase, ensuring 100% modulation of W radiation on a
- frequency of 100 Hz. The laser emission signal indicates a spiked mode of lasing.
The time intervals of 1-2 ms when lasing is absent correlate with pumping. Lasing
usually appears when pumping reaches a level of 50% of the maximum power. Laser
resonator losses were estiamted in expPriments with a xenon flash tube ITI'-2000
- placed close to the laser Lube, from the change in delay of the beginning of lasing
and emission power when a thin quartz plate was inserted in the cavity. According
to the~e data, losses amounted to 3% per round trip. This shows that the unsaturated
gain corresponds to 6% per pass in the maxima of pumping radiation.
The quantity y was determined from the signal of photocell F-7 with known absolute
sensitivity on the 254 nm line. For the conditions of our experiments it was
_ 0.05 � 0.02 s'1. In doing this, the lamps were placed on opposite sides of the
laser tube at a distance of 3 mm away, and the illuminator was practically unused.
We can easily convince ourselves that the measured saturated gain is close to the
calculated val.ue (see the data of the table for experiments 1 and 4). We need
only consider the reduction in vo t with heating (see experiments 7-9) and the
fact that the gas used was not entirely free of quenchants. This is shown by mea-
surements of the lifetime of atoms of I* made to check the purity of the working
gas by means of device 7(see Fig. 2) from attenuation of luminescence on a= 1315
nm. These measurements gave a value of the rate constant k5 that was double the
value obtained in Ref. 8. Under the conditions of the given laser system we rarely
managed to purify the working gas to give values of k5 close to those quoted in
the literature [Ref. 8, 9], and it required a great deal of time.
4. Discussion of the Results
The data given above show that the duration of cw lasing on a= 1315 nm that we
observed in the mode of single passage of the working gas through the laser tube
is approximately two orders of magnitude greater than the duration of continuous
lasing observed in Ref. 6 on (CF3)3CI. This difference is partly due to the fact
that the latter has a much lower saturated vapor pressure at room temperature than
CP3I. For an identical supply of both gases, (CF3)3CI requires a much larger
volume. For use as an intermediate quantum frequency standard [Ref. 16], the pos-
_ sible lasing duration must be much longer than that which we have achieved. The
results described above confirm our estimates of the feasibility of achieving cw
emission without replenishment of the working gas for a considerably longer time
when cyclic circulation of the gas in a closed system is used with a cooler for
removing the molecular iodine that is the only harmful photolysis product. These
estimates show that under the conditions of experiment 4(see the table) over an
illumination time of 40 ms (~~toPt) in the absence of lasing the irreversible con-
sumption of working gas is 0.065/ (final products I2 and C2F6), i. e. 33% of the
degree of photodissociatio~i y~t= 0.2%.
In experiments without lasing for similar conditions, an amount of molecular iodine
corresponding to an irreversible consumption of 0.088% was determined by distillation
30
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and weighing. It can be expected [Ref. 17J that under conditions of laser emission
the irreversible consumption will be considerably reduced. But even if this does
not happen, the estimate od continuous lasing time ~t~ under conditions of cyclic
_ circulation with the same amount of gas supply (43.5 g) and the same values of
velocity and pressure in the laser pumping tube and ~Z gives ~t~ > 100 minutes if
we assume that the time of one cycle ~tl = 1 minute, and the number of cycles m> 100
corresponds to 10% irreversible consumption of working gas at a consumption of