Kinetics of vibrationally-excited singlet oxygen O2(a1Δ,ν) in gas mixture O3/N2/CO2 was studied using a pulse laser technique. Molecules O2(a1Δ,ν) were produced by laser photolysis of ozone at 266 nm. The O3 molecules number density was followed using time-resolved absorption spectroscopy. It was found that an upper bound for the rate constant of chemical reaction O2(a1Δ,ν)+ O3 is about 10-15 cm3/s. The rate constants of O2(a1Δ,ν= 1, 2 and 3) quenching by CO2 are presented.
The mandatory condition for efficient operation of an optically-pumped all-rare-gas laser (OPRGL) is the presence of rare gas metastable atoms in the discharge plasma with number density of the order of 1012-1013 cm-3. This requirement mainly depends on the choice of a discharge system. In this study the number density values of argon metastable atoms were obtained in the condition of the dielectric-barrier discharge (DBD) at an atmospheric pressure.
Kinetics of vibrationally-excited singlet oxygen O2(a1Δ,v) molecule have been examined using pulsed laser technique.O2(a1Δ,v) molecules were produced by the pulsed 266 nm laser photolysis of ozone. The kinetics of O2(a1Δ) quenching were followed by observing the 1268 nm fluorescence of the O2 a1Δ-X3Σ transition. It has been found that the loss of O2(a1Δ,v) in the O(3P)/O3/N2 mixture is carried out both in chemical and in V-T process. We observed that the vibrational excitation of singlet oxygen molecule enhances the rate of reaction between O2(a1Δ,v) and O3 molecules. The rate constant of this process was estimated to be in the range 10-12-10-11 cm3/s. Rate constant of O2(a,v=1) quenching by CO2 was found to be (1.03±0.07)×10-14 cm3/s.
This paper describes systematic measurements of pressure broadening coefficients for argon and krypton lines in an RF (radio-frequency) discharge plasma sustained in a mixture of inert gases. Using tunable diode laser spectroscopy we obtained experimental data for pressure broadening of argon and krypton lines. Pressure broadening coefficients were determined for Ar+Ne and Kr+Ne and Kr+Ar. For krypton, the isotopic structure of the line was taken into account and an appropriate fitting function was used to determine pressure broadening coefficients for the natural mixture of isotopes. These data may be used for diagnostics of the active medium of optically pumped all-rare-gas lasers.
Optically pumped all-rare-gas laser (OPRGL) with unique properties was recently proposed. To study this promising laser system it is necessary to have reliable diagnostics for the active medium. A set of pressure broadening coefficients, for self- and foreign- gas collision partners, is needed for measurements of the number density of metastable atoms and temperature in a rare gas discharge plasma by means of spectroscopy. However, literature analysis had shown that pressure broadening coefficients for rare gas lines in mixtures that are of interest for OPRGL’s are surprisingly hard to find, or were not yet measured. Diode laser absorption spectroscopy was employed for measurements of pressure broadening coefficients for the Krypton 811.3 nm line in an RF discharge. A multi-quantum well diode laser (L808P030, Thorlabs) with an original short external cavity was used as a source of probe radiation. The natural isotopic distribution of Kr was taken into account, and an appropriate fit function was constructed. This permitted the determination of pressure broadening coefficients using the natural mixture of isotopes. The coefficients for the Kr 811.3 nm line at 300 K, measured for the first time, were ξKr-Ne = (1.50 ± 0.05) ×10-10 s-1cm3 for broadening by Neon, and ξKr-Ar = (3.5 ± 0.3) ×10-10 s-1cm3 for broadening by Argon.
KEYWORDS: Oxygen, Iodine, Molecules, iodine lasers, Chemical lasers, Gas lasers, Optical pumping, Chemical species, Active optics, Chemical oxygen iodine lasers, Laser optics, Semiconductor lasers, Aerospace engineering, Laser systems engineering
The kinetics of the processes in an O2/I2/Ar/H2O gas flow that is irradiated simultaneously by light at wavelengths near 500 nm and 1315 nm, is considered. Radiation at 500 nm is used to photodissociate about 1% of the iodine molecules. The radiation at 1315 nm excites atomic iodine to the 2P1/2 state. Singlet oxygen molecules are produced via the energy exchange process I(2P1/2)+O2(X3Σ) → I(2P3/2) + O2(a1Δ), while I(2P1/2)+O2(a1Δ) energy pooling produces b1Σ oxygen. I(2P1/2) and O2(b1Σ) then accelerate the dissociation of I2. This active medium may reach ~40 W/cm–2 at an optical efficiency of 50%.
Experiments and modeling of CH3I dissociation in the plasma generated by a 40 MHz RF discharge were performed. A discharge chamber of an original design, consisting of quartz tubes between two planar electrodes, permitted the production of iodine atoms with number densities up to 2×1016 cm-3. In this discharge chamber, contamination of the walls of the tubes did not hinder discharge stability, providing a good iodine production rate. Addition of oxygen into Ar:CH3I mixture resulted in a substantial increase in iodine extraction efficiency. When the discharge power reached 200 W, complete CH3I dissociation in a Ar:CH3I:O2 mixture was observed. The fraction of discharge power spent on iodine atom production at a 0.17 mmol/s CH3I flow rate was 16%.
Alkali vapor lasers commonly use methane (CH4) or ethane (C2H6) to induce energy transfer between the optically pumped level (n2P3/2) and the upper laser level (n2P1/2). A complication is that the alkali metal eventually reacts with the hydrocarbons. The reaction becomes exothermic for alkali atoms that have been excited by energy pooling processes such as Rb(5p)+Rb(5p)→Rb(*)+Rb(5s), where * indicates 6s, 6p or 4d. We have used laser pump-probe methods to examine the reactions of Rb(n2P) with CH4, and C2H6 for states with n=6 and 7. Pump-probe measurements indicated a loss of Rb due to a reaction. Surprisingly, the RbH product was not detected with CH4, and C2H6. High-level ab initio calculations have been used to study the reactive interactions between Rb, methane and ethane.
The development of a discharge oxygen iodine laser (DOIL) requires efficient production of singlet delta oxygen O2(α1 Δ) in electric discharge. It is important to understand the mechanisms of of O2α1 Δ) quenching in these devices. To gain understanding of this mechanisms quenching of O2(α]1 Δ)in O/O2/O3/CO2/He mixtures has been investigated. Oxygen atoms and singlet oxygen molecules were produced by the 248 nm laser photolysis of ozone. The kinetics of O2(α1 Δ) quenching were followed by observing the 1268 nm fluorescence of O2α1 Δ → X3 Σ transition. It is shown that vibrationally excited ozone O3(υ;) formed in the three-body recombination O + O2 + M →O3(υ) + M is an important O/O2/O3 quenching agent in O/O2/O3 systems. The process O3(υ ≥2) + O2(a1 Δ)→ 2O2 + O is the main O2(α1 Δ) deactivation channel in the post-discharge zone. If no measures are taken to decrease oxygen atom concentration, the contribution of this process into overall O2(α1Δ) removal is significant even in the discharge zone. It was found in experiment that addition of species that are good quenchers of O3(υ;) decrease O2(a1 Δ) deactivation rate in the O/O2/O3 mixtures.
Results of experiments and modeling of CH3I dissociation in a 40 MHz RF discharge in a discharge chamber of original design to produce iodine atoms for cw oxygen-iodine laser are presented. In experiments a substantial increase in CH3I dissociation efficiency due to addition of oxygen into Ar:CH3I mixture was observed. Complete CH3I dissociation in Ar:CH3I:O2 mixture occurred at 200 W discharge power. Fraction of discharge power spent on iodine atoms production was equal to 16% at 0.17 mmol/s CH3I flow rate. The rate of carbon atoms production as a function of molecular oxygen and water contents in CH3I:Ar mixtures was studied with the help of numerical modeling. It was found that addition of water vapor resulted in increase while addition of molecular oxygen and HI in decrease of the rate of carbon atoms production. Due to diffusion most of carbon atoms had enough time to deposit on the walls of the discharge chamber. However, contrary to the situation in a DC discharge, in the RF discharge accumulation of carbon on the walls of the discharge chamber did not hamper discharge stability and iodine production, as it was observed in our experiments.
The single-frequency two-level (SFTL) generation model was applied to predict the power extraction efficiency in electrically driven oxygen-iodine laser (EOIL). The analysis of the calculated and published experimental data showed that power extraction from the cw EOIL is limited by the rate of energy transfer from singlet oxygen molecules O2(1Δ) to iodine atoms I(2P3/2) and about half of the produced singlet oxygen molecules were carried out from the resonator. To increase power extraction efficiency it will be necessary to substantially extend concentrations of singlet oxygen molecules and iodine atoms in the active medium of EOIL.
A simplified two-level generation model predicts that power extraction from an cw oxygen-iodine laser (OIL) with stable resonator depends on three similarity criteria. Criterion τd is the ratio of the residence time of active medium in the resonator to the O2(1Δ) reduction time at the infinitely large intraresonator intensity. Criterion Π is small-signal gain to the threshold ratio. Criterion Λ is the relaxation to excitation rate ratio for the electronically excited iodine atoms I(2P1/2). Effective power extraction from a cw OIL is achieved when the values of the similarity criteria are located in the intervals: τd=5-8, Π=3-8 and Λ≤0.01.
Usage of an external iodine atom generator can improve energy efficiency of the oxygen-iodine laser (OIL) and expand
its range of operation parameters. However, a noticeable part of iodine atoms may recombine or undergo chemical
bonding during transportation from the generator to the injection point. Experimental results reported in this paper
showed that uncoated aluminum surfaces readily bounded iodine atoms, while nickel, stainless steel, Teflon or Plexiglas
did not. Estimations based on experimental results had shown that the upper bound of probability of surface iodine atom
recombination for materials Teflon, Plexiglas, nickel or stainless steel is γrec ≤ 10-5.
KEYWORDS: Oxygen, Molecules, Iodine, Carbon dioxide, Chemical oxygen iodine lasers, Nitrous oxide, Chemical species, Chemical lasers, Data modeling, Energy transfer
Kinetic data obtained in the last decade has resulted in revisions of some mechanisms of excitation and deactivation of
excited states in the chemical oxygen-iodine laser (COIL) medium. This review considers new kinetic data and presents
analyses of the mechanisms of pumping and quenching of electronically and vibrationally excited states in the oxygen-iodine
laser media. An effective three-level model of I2 molecule excitation and relaxation has been developed. The
calculated effective rate constants for deactivation of I2(X,11&leνle;24) by O2, N2, He and CO2 are presented. A simplified
kinetic package for the COIL active medium is recommended. This model consists of a 30-reaction set with 14 species.
The results of calculations utilizing simplified model are in good agreement with the experimental data.
The development of a discharge oxygen iodine laser (DOIL) requires efficient production of singlet delta oxygen (O2(a))
in electric discharge. It is important to understand the mechanisms by which O2(a) is quenched in these devices. To gain
understanding of this mechanisms quenching of O2(a) in O(3P)/O2/O3/CO2/He/Ar mixtures has been investigated.
Oxygen atoms and singlet oxygen molecules were produced by the 248 nm laser photolysis of ozone. The kinetics of
O2(a) quenching were followed by observing the 1268 nm fluorescence of the O2a → X transition. Fast quenching of
O2(a) in the presence of oxygen atoms and molecules was observed. The mechanism of the process has been examined
using kinetic models, which indicate that quenching by vibrationally excited ozone is the dominant reaction.
Experiments were carried out with a subsonic chemical oxygen-iodine laser (COIL), equipped with an electric discharge
generator of iodine atoms. CH3I entrained in a carrier flow of Ar was used as atomic iodine precursor. About 50% of
iodine contained in CH3I molecules was extracted in the generator. Up to 3.5% of electric power loaded into the
discharge was spent on CH3I dissociation. A straightforward comparison of COIL performance for two cases -
conventional, when I2 was injected in the singlet oxygen flow and when iodine atoms produced externally together with
other discharge products were injected - was made. In the latter case nearly four times increase in output power was
observed.
A new kinetic scheme for the dissociation of I2 by O2(a) has been proposed by Azyazov et al. (J. Chem. Phys. 130,
104306/9 (2009)). In principle, the reactions initiated by UV photolysis of N2O/I2 mixtures can be used to probe the
chain propagation stage of this dissociation model, and provide additional validation. In the present study, 193 nm laser
photolysis of N2O/I2 mixtures was used to initiate secondary chemical reactions and to produce iodine atoms. Singlet
oxygen was generated in this system by the fast reaction O(1D)+N2O→ O2(a)+N2. Emission spectroscopy and laser
induced fluorescence techniques were used to follow the time evolutions of I* and I2. The photolysis of N2O/I2 mixtures
creates all of the species needed to sustain the chain propagation stage of I2 dissociation process. However, it was found
that the high pressures of N2O needed to generate sufficient concentrations of O2(a) suppressed the I2 dissociation
process. Computational modeling indicated that suppression of the chain propagation reactions under the conditions
examined was consistent with the revised dissociation model.
The development of discharge singlet oxygen generators (DSOG's) that can operate at high pressures is required
for the power scaling of the discharge oxygen iodine laser. In order to achieve efficient high-pressure DSOG
operation it is important to understand the mechanisms by which singlet oxygen (O2(a1Δ)) is quenched in these
devices. It has been proposed that three-body deactivation processes of the type O2(a1Δ))+O+M→2O2+M
provide significant energy loss channels. To further explore these reactions the physical and reactive quenching
of O2(a1Δ)) in O(3P)/O2/O3/CO2/He/Ar mixtures has been investigated. Oxygen atoms and singlet oxygen
molecules were produced by the 248 nm laser photolysis of ozone. The kinetics of O2(a1Δ)) quenching were
followed by observing the 1268 nm fluorescence of the O2 a1Δ-X3Ε transition. Fast quenching of O2(a1Δ)) in the
presence of oxygen atoms and molecules was observed. The mechanism of the process has been examined using
kinetic models, which indicate that quenching by vibrationally excited ozone is the dominant reaction.
KEYWORDS: Oxygen, Carbon dioxide, Iodine, Chemical oxygen iodine lasers, Molecules, Data modeling, Chemical lasers, Systems modeling, Chlorine, Laser induced fluorescence
An advanced kinetic package for COIL is proposed. The standard kinetic package was revised by adding processes describing the vibrational excitation and relaxation kinetics of I2 and O2. A multi-pathway I2 dissociation mechanism and new kinetic data are key elements of the advanced kinetic package.
Concentration of iodine molecules at the outlet of an electric discharge iodine atoms generator was measured using
laser-induced fluorescence. Methyl iodine was used as an iodine atom precursor. Fraction of iodine extracted from
CH3I in the discharge generator was about 50%. Optimal mode of operation at which 80-90% of total extracted iodine
was in the form of iodine atoms was found. Iodine atom content in the gas flow decreased during transportation down to
20-30% at the point of iodine injection into the oxygen flow. Fraction of power load spent on CH3I dissociation
amounted to ≈3%.
Vibrationally excited iodine I2(X,v>20) is an important intermediate in the standard COIL dissociation model. This intermediate is populated by the I* + I2(X) reaction. In this model excitation probabilities for the v-th I2(X) vibrational level γ(v) are critical parameters. In the present study we examined excitation probabilities γ(v) based on the comparison of calculated populations of vibrational levels of iodine molecules with their experimental values. The total excitation probability for I2(X, v>25) was found to be γ(v>25)≈ 0.1. The standard dissociation model with γ(v>25) ≈0.1 cannot provide the observed dissociation rates. Moreover the number of O2(a) molecules consumed per dissociated I2 molecule would exceed 20 if the standard dissociation model is the predominant dissociation pathway, which is at variance with experiment.
Barnault et al.3 found that the populations of I2(10≤v≤23) were much higher than ν≥30. Such high populations of I2(10≤v≤23) could be explained by means of direct excitation in the I* + I2(X) reaction. A satisfactory agreement between calculated I2(v) populations and the experimental data was achieved for the total excitation probability γ(v>25) =0.05-0.1 and for γ(15
Kinetic model of I2 molecule dissociation in a COIL medium involving vibrationally and electronically excited iodine and oxygen molecules was developed. The current understanding of the problem of the iodine dissociation mechanism in the COIL medium is described.
Experiments with a flow cell apparatus imitating conditions of oxygen-iodine laser, equipped with a chemical jet singlet oxygen generator and an electric discharge iodine generator have been performed. I2 and CH3I in the flow of Ar were used as atomic iodine precursors.
The distributions of the electronically excited species along the flow were examined detecting their optical emissions. A straightforward comparison of two methods of oxygen-iodine medium production - conventional, by means of I2 dissociation in the singlet oxygen flow and with iodine atoms produced externally in the electric discharge - was performed.
It was found that stored electron energy lifetime had been about 30% longer, when iodine was produced from CH3I in the discharge, compared to the conventional I2 dissociation in the singlet oxygen flow. It was observed that maximums of the I(2P1/2) and I2(B) concentrations had shifted to the nozzle plane, when I2 in Ar carrier was subjected to the glow discharge, pointing to a nearly twofold increase in the I2 dissociation rate. Contrary to the known results for low iodine and singlet oxygen concentrations, squared dependence of the amplitude of the I2(B) luminescence maximum with I(2P1/2) concentration was observed in the dissociation region for both methods of iodine production.
Oxygen-iodine lasers that utilize electrical discharges to produce O2(a1Δ) are currently being developed.
The discharge generators differ from those used in chemical oxygen-iodine lasers in that they produce
significant amounts of atomic oxygen and traces of ozone. As a consequence of these differences, the
chemical kinetics of the discharge laser are markedly different from those of a conventional chemical
oxygen-iodine laser (COIL). The reactions of O with iodine include channels that are both beneficial and
detrimental to the laser. The beneficial reactions result in the dissociation of I2 while the detrimental
processes cause direct and indirect removal of I(2P1/2) (denoted I*, the upper level of the laser). We have
examined kinetic processes relevant to the laser through studies of photo-initiated reactions in N2O/CO2/I2
mixtures. The reactions have been monitored using absorption spectroscopy, laser induced fluorescence
and time-resolved emission spectroscopy. It has been established that deactivation of I* by O atoms is a
critical energy loss process. We have determined a rate constant of (1.2±0.1)×10-11 cm3 s-1 for this reaction.
As part of this effort the branching fraction for the formation of O2(a) from the reaction of O(1D) with N2O
was determined to be 0.38. This result has implications for lasers based on photolysis of O3/N2O/I2
mixtures and the formation of O2(a) in the upper atmosphere.
The efficient power operation in a chemical oxygen-iodine laser for subsonic modes has been demonstrated. It is
shown that the substitution of the buffer gas N2 by CO2 does not cause any significant variation in the dependence of the
output power on the degree ofdilution ofthe active medium. The maximum power was 581 W for the flow rate of molecular
chlorine 22 mmole/s that corresponds to a chemical efficiency of &eegr;chem = 29%.
The kinetic model of I2 molecules dissociation in chemical oxygen iodine laser (COIL) medium taking into
account interaction of the vibrationally excited iodine and singlet oxygen molecules is developed. The results of
computer calculations utilizing this model are good agreement to experimental dissociation rate of iodine molecules in
the media characteristic of COIL.
In the present study we have observed rapid quenching of O2(a1&Dgr;) in O(3P)/O2/O3 mixtures. Oxygen atoms and
singlet oxygen molecules were produced by the 248 nm laser photolysis of ozone. The kinetics of O2(a1&Dgr;)
quenching were followed by observing the 1268 nm fluorescence of the O2a1&Dgr;-X3&Sgr; transition. The temporal
profiles of oxygen atoms O(3P) were monitored by means of the O+NO chemiluminescent reaction. The
mechanisms of fast O2(a1&Dgr;) quenching in the presence of O atoms are discussed.
The mechanism by which I2(B) is excited in the chemical oxygen-iodine laser was studied by means of emission
spectroscopy. Using the intensity of the O2(b1&Sgr;,&ngr;'=0) → O2(X3&Sgr;,&ngr;''=0) band as a reference, I2(B) relative number densities were assessed by measuring the I2(B,&ngr;')→ I2(X,&ngr;") emission intensities. Vibrationally excited singlet
oxygen molecules O2(a1&Dgr;, &ngr;'=1) were detected using IR emission spectroscopy. The measured relative density of O2(a1&Dgr;,&ngr;'=1) for the conditions of a typical oxygen-iodine laser medium amounted to ~15% of the total O2 content. Mechanisms for I2(B) formation were proposed for both the I2 dissociation zone and the region downstream of the dissociation zone. Both pumping mechanisms involved electronically excited molecular iodine I2(A', A) as an intermediate. It has been suggested that, in the dissociation zone, the I2 A', and A states are populated in collisions with vibrationally excited singlet oxygen molecules O2(a1&Dgr;,&ngr;'). In the region downstream of the dissociation zone the intermediate states are populated by iodine atom recombination process. I2(B) is subsequently formed in collisions of I2(A',A) with singlet oxygen. We also conclude that I2(B) does not participate measurably in the I2 dissociation process and that energy transfer from O2(b1&Sgr;) does not excite I2(B) to a significant degree.
Oxygen-iodine lasers that utilize electrical or microwave discharges to produce singlet oxygen are currently being developed. The discharge generators differ from conventional chemical singlet oxygen generators in that they produce significant amounts of atomic oxygen. Post-discharge chemistry includes channels that lead to the formation of ozone. Consequently, removal of I(2P1/2) by O atoms and O3 may impact the efficiency of discharge driven iodine lasers. In the present study we have measured the rate constants for quenching of I(2P1/2) by O(3P) atoms and O3 using pulsed laser photolysis techniques. The rate constant for quenching by O3, 1.8x10-12 cm3 s-1, was found to be a factor of five smaller than the literature value. The rate constant for quenching by O(3P) was 1.2x10-11 cm3 s-1. This was six times larger than a previously reported upper bound, but consistent with estimates obtained by modeling the kinetics of discharge-driven laser systems.
A1GaAs/GaAs quantum-well diode laser (824 nm) with the short external cavity was used for water diagnostics in the pumped out gas cell. The laser provided the 63 GHz continuous tuning of the optical frequency by the scanning of a pump current and a spectral linewidth of oscillation was less than 0,2 GHz. The experimentally obtained dependence of a second derivative amplitude on the vapour pressure coincides well with the calculated curve in the range of 0,4-20 Torr. The change of output signal close to linear was recorded at a pressure in the sample gas cell less than 5 Ton. The minimum concentration of H20, which is still measured by the diode laser sensor is estimated at a level 1,5x1015 molecule/cm3.
KEYWORDS: Oxygen, Molecules, Chemical oxygen iodine lasers, Chemical lasers, Iodine, Molecular lasers, Chemical analysis, Chemical species, Luminescence, Emission spectroscopy
The analysis of a luminescence spectra of oxygen molecules on O2(b1Σg,υ’)→O2(X3Σg-υ") transitions has shown, that vibrationally excited O2(b1Σg+) molecules up to υ=5 are generated in the active medium of chemical oxygen-iodine laser (COIL). Comparison of experimental and calculated results has shown that 4.5 vibrational quanta of oxygen are formed in the active medium of COIL under the deactivation of one singlet oxygen molecule. Dependencies of the threshold of O2(α1Δg) yield and gain on relative population of vibrationally excited oxygen are studied. The threshold of O2(α1Δg) yield increases with rising of the relative population of vibrationally excited oxygen and can be some percents more than it was considered before. The gain coefficient weakly depends on the relative population of vibrationally excited oxygen.
The vibrationally excited oxygen in O2(a1Δg)-I mixture was detected by emission spectroscopy. The analysis of a luminescence spectra of oxygen molecules on O2(b1Σg+,υ') → O2(X3Σg-,υ") transitions has shown, that vibrationally excited O2(b1Σg+) molecules up to υ=5 are generated in the active medium of chemical oxygen-iodine laser (COIL). The highest values of relative O2(b1Σg+,υ=1) population of 22% and O2(b1Σg+,υ=2) of 10% are reached for I2 content in an oxygen flow ≈1%. It is shown theoretically, that the relative populations of O2(X3Σg-), O2(a1Δg) and O2(b1Σg+) molecules at the first and the second vibrational levels are approximately equal because of fast EE energy exchange between oxygen molecules. Up to 20% of oxygen molecules in COIL active medium are vibrationally excited.
KEYWORDS: Oxygen, Molecules, Chemical lasers, Chemical oxygen iodine lasers, Iodine, Molecular lasers, Energy transfer, Temperature metrology, Lithium, Resonance energy transfer
The kinetics model of chemical oxygen-iodine laser (COIL) active medium taking into account EE, EV, VV, VT energy transfer processes was proposed. The O2 molecule distribution on the vibrational levels in COIL was calculated. It is suggested that the involving of vibrationally excited O2(a) into pooling reaction can increase the rate of stored in singlet oxygen electronic energy in COIL medium. Approximately 50% of relaxed O2(a) energy transfers into thermal energy.
It is experimentally shown that more than 20% of O2 molecules in chemical oxygen iodine laser (COIL) active medium are vibrationally excited. Calculations show that approximately 4.5 vibrational quanta are formed under deactivating of one singlet oxygen O2(1Δ) molecule. Dependencies of threshold O2(1Δ) yield and gain on relative population of O2(1Δ,υ) are presented. The threshold O2(1Δ) yield increases with rising of the relative population of vibrationally excited oxygen and it can be some percents more than was considered before. The gain coefficient of COIL weakly depends on the degree of vibrational excitation of oxygen.
Efficient subsonic chemical oxygen iodine laser operating with small buffer gas flow rate at Mach number M<EQ1 is reported. The highest value of output power of 415 W with chemical efficiency 23% was obtained at Cl2 flow rate of 20 mmole/s. It was found that the power does not almost depend on N2 or CO2 buffer gas flows up to two times higher than oxygen flow rate.
KEYWORDS: Oxygen, Molecules, Iodine, Chemical lasers, Energy transfer, Chemical oxygen iodine lasers, Molecular energy transfer, Information operations, Molecular lasers, Molecular spectroscopy
Relaxation of the electronic energy in the active medium of the chemical oxygen-iodine laser (COIL) causes non- equilibrium population of vibrational levels of oxygen. It is found that the fraction of vibrationally excited oxygen can reach several of percent in the oxygen stream. The rate relaxation of vibrational energy of oxygen is limited by the exchange between oxygen at the first vibrational level and the bending mode of water. A simple formulas for the population of singlet oxygen vibrational levels at the output of a singlet-oxygen generator are found. It is noted that the EE energy transfer between singlet oxygen and molecular iodine stimulated by the vibrational excitation may be of considerable importance in the kinetics of iodine dissociation.
The relaxation of electronically excited oxygen in the active medium of chemical oxygen- iodine laser (COIL) may cause a nonequilibrium population of O2 and I2. Previously it has been the subject of theoretical study. The authors of this study suggest that the vibrationally excited oxygen molecules of O2(1(Delta) ,v) may take part in the I2 dissociation. In this work the vibrational population of O2 molecules in the COIL active medium was calculated. The O2 vibrational populations are obtained under the typical lasing conditions. The gaseous medium of COIL consists of O2, O2(1(Delta) ), I, I2, H2O, Ar. It is assumed that the chemical generator of singlet-delta oxygen is used. In this case the molecules of H2O play the important role in kinetics of the vibrationally excited oxygen molecules.
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