The capability of remote-sensing measurements of the stratosphere in the submillimetric spectral region is presented. The analysis is discussed of spectra recorder by a balloon-borne Fourier Transform spectrometer that measures the emission of the atmosphere in the submillimetric with the limb-scanning observation technique. Two problems, that have been studied with submillimetric spectroscopy, are presented in detail: the measurement of HBr and the diurnal variability of hydroxyl radical.

We report on recent advances of laser spectroscopic schemes applied to air pollution monitoring. All systems presented are based on tunable narrowband infrared sources including a conventional line-tunable CO₂ laser, a continuously tunable high-pressure CO₂ laser, an optical-parametric- oscillator-based difference-frequency (DFG) laser and a diode-based DFG laser. These systems cover the mid-infrared wavelength range important for fundamental molecular absorptions. Gas detection is performed with a multipass transmission cell, with specially designed photoacoustic cells using resonant and nonresonant configurations with a single microphone or multi-microphone arrays or with a photothermal arrangement sensing the temporal change of the refractive index. The performance of these systems is illustrated with various examples of trace gas monitoring on the one hand and determination of molecular relaxation rate constants on the other hand with the photothermal scheme. In many cases detection limits corresponding to minimum concentrations in the ppb (10^-9, nmole/mole) or even sub-ppb level are achieved. It is demonstrated that this kind of laser spectrometers offer easiness of operation (room temperature, neither sample preparation nor pretreatment, portability), excellent sensitivity and selectivity, large dynamic range (up to 7 orders of magnitude) and good temporal resolution.

The investigations on Intracavity Laser (ICL) spectroscopy performed during 30 years are overviewed in the paper. Some basic results in theory, in the extraction information on absorption line parameters, different constructions of the ICL-spectrometers are presented. Different applications of the method based on its high sensitivity to absorption are discussed.

Carbon dioxide gas is recognized among principal absorbers of radiation in the Earth's atmosphere. Moreover, carbon dioxide molecules are ubiquitous in the Universe. Being a dominant gas phase constituent in the atmospheres of Mars and Venus, carbon dioxide is responsible for a variety of physico-chemical processes in atmospheres of these terrestrial group planets. Weak intermolecular interaction among carbon dioxide molecules results in formation of van der Waals complexes or dimers. Estimates show that (CO₂)₂ dimers are the most abundant constituent in the surface layers of Venusian atmosphere after CO₂ itself. Although carbon dioxide in the gas phase is not appreciably abundant in the interstellar media, recent spectroscopic observations provide strong indications of widespread CO₂-ices and CO₂-rich ice mantles in molecular clouds. All these justify carrying out extensive experimental and theoretical studies of the carbon dioxide molecules in pairwise and higher order interactions. Crucial role in these investigations belongs to laboratory spectroscopic studies which imply a variety of methods, tools and external parameters. Present paper aims at reviewing infrared and Raman spectroscopy of CO₂ dimers formed in adiabatically cooled flows, in a pressurized static gas sample, and while trapped in low-temperature matrices.

For remote-sensing of atmospheric trace gases using optical spectroscopy, accurate reference spectra from the laboratory are essential. In this paper, recent work on a number of important atmospheric molecules and radicals is reviewed. Particular focus is made on the spectral regions covered by new-generation satellite spectrometers, in particular by the GOME and SCIAMACHY instruments operating in the UV-visible and near-infrared (230 - 790 nm and 215 - 2385 nm, respectively.

The results of experimental and theoretical studies of the influence of large amplitude motions of nuclei on the IR and Raman spectra, electrooptical parameters, and structural features of molecular systems in various stages of aggregation are generalized. The mechanisms of intramolecular rearrangements in these systems are considered. The potential of the finite element method for the description of the large amplitude motions of arbitrary form is demonstrated. A method for estimation of the characteristic time of intramolecular rearrangements is proposed.

One of the possible ways to analyze rotational dynamics of molecules in case when the ro-vibrational interaction can not be considered as a small one is discussed in this paper. In the method proposed the most part of the ro-vibrational interaction is taken into account in zero-order approximation. Applied to the number of real molecular ro- vibrational problems, this approach has been proved to be a sufficiently powerful tool for rotational dynamics qualitative analysis and then for revealing rotational multiplet structure. It also can be considered as a base for quantum rotational energy levels calculations.

The bifurcation in the rotational dynamics of triatomic nonsymmetrical hydrides is studied within the framework of microscopic approach. Our method proposed earlier is used for Rotational Energy Surface construction. Critical values of angular momentum for some HDX molecules (X equals O, S, Se, Te, ...) are first calculated.

In this paper we present the expressions that have been derived using the Lorentz-Lorenz formula of the dispersion theory and which enable one to calculate the real and imaginary parts of the dielectric constant and refractive index of an arbitrary gaseous mixture. The calculations use experimental data on the absorption spectra of the mixture. These values may be calculated as functions of the incident radiation frequency, including spectra regions involving the absorption lines and bands. We have shown in our study that the absorption line contour that follows from the dispersion theory dose not coincide with the Lorentz contour. We propose that the line contour considered in this paper be called as the Lorentz-Lorenz contour to distinguish it from the Lorentz one.

The first order Coriolois resonance between nondegenerate v_s and degenerate v_t fundamentals of symmetric polyatomic molecules give rise to the doubling of the sublevels of mode v_t with values of quantum number k equals l equals 1 of the projection of full angular momentum and vibrational momentum of double degenerate mode v_t. In dominant approximation the energy splitting dependent lineary on the quantum number of full angular momentum J. Effective Hamiltonian for giant l-doubling in symmetric molecules has been developed on the base of theory of linked ordering schemes of rovibrational interactions. Theory of non-linear sequence transformation is applied for the analysis of obtained approximation series on J².

The aim of the work is to apply multifractal analysis to absorption spectra of basic molecules of the atmosphere H₂O, CO₂, O₃. We have shown that the absorption spectra of vibration-rotation bands of gas molecules possess nontrivial multifractal features. The spectrum of multifractal dimensions is generated by the `absorption density' (the normalized summary absorption per the unit of spectral interval). The singularity spectrum depends on molecular and isotopic composition of gas and of type of vibration-rotation band of absorption.

New analysis is performed of a body of data on v₂ band line intensities of the water molecule involving mainly the transitions reported by R. A. Toth. As a theoretical approach the formalism of the effective-dipole moment operators is used. We have been able to determine eight effective-dipole moment parameters, which result in a satisfactory agreement between observed and calculated intensities. The total RMS deviation of the fit is 6%.

Second-order corrections on m_e/M_i in effective vibration-rotation Hamiltonian and in Dunham coefficients were calculated for diatomic molecules in ¹(Sigma) electronic state.

A stationary distribution of populations in a three-level quantum system interacting with three intense monochromatic fields resonant to two allowed and one forbidden transition is determined for three possible configurations of the considered system. The obtained algebraic expressions for populations of levels are exact within the frameworks of RWA and dependent on the phases of fields even in the limit of strong field intensities. The latter circumstance causes the absorption line profile to be noisy due to random phase modulation of fields. The sets of parameters of the system and field are founded at which the populations of all the levels are equal to 1/3 also with the regions where a resonance-like dependence of level populations on the difference of field phases takes place.

The temperature dependence of polarizabilities of gaseous N₂ and O₂ in a wide temperature range was calculated. These calculations are based on the experimental values of polarizability derivatives. The temperature dependence obtained has been given in a simple form.

The equilibrium structures and molecular properties of S₀ and S₁ states of (H₂O...HF)_n, n equals 1 - 5, complexes were calculated at ab initio SCF and ROHF levels with use of the MONSTERGAUSS program. Analysis of electron density distribution for S₀ and S₁ states were performed. The excitation energies of S₀ yields S₁ transitions for (H₂O...HF)_n, n equals 1 - 5, complexes were determined. The influence of hydrogen bond formation on the shift in the maximum of first absorption band of these complexes was examined. The investigations of electronic excited states of molecules allow solving some analytical problems. One of them it is a problem about identification of substances. In virtue of data about electronic excited states it is possible to carry out a study of photophysical and photochemical processes what take place after photon absorption. From an analysis of experimental data follow that formation of intermolecular hydrogen bond results in the shifts of absorption bands. The shift depends from type of electronic transition. The investigation of the nonrigid molecular complexes is important for atmospheric spectroscopy purposes.

The effective operator approach is applied for the global fitting of the vibrational-rotational line positions of acetylene molecule. About 4470 line positions of the transitions involving vibrational-rotational energy levels up to 4200 cm^-1 have been used to determine 130 parameters of the effective Hamiltonian. The standard deviation of the fit is 0.0009 cm(superscript -1$.

The contribution have been devoted the construction of effective quadrupole coupling operator for quasidegenerate vibrational levels of polyatomic molecules and the reduction of the laser. The indeterminacy problem of the parameters in the effective vibrational-rotational H^eff_VR and quadrupole W_eff Hamiltonians for the cases of accidental resonances linked with various groupings of vibrational- rotational interactions (problem of grouping uncertainty) are considered. The problem of the reduction of H^eff equals H^eff_VR + W^eff is discussed. The case of the Coriolis-type, accidental resonances have been considered more detail. New representation of H^eff equals H^eff_VR + W^eff for isolated vibration levels in form of angular moments only is presented.

Various empirical and ab initio potential energy surfaces (PES) of ozone are compared with recent accurate PES obtained by a variational fit to spectroscopic data. The value of the dissociation energy D_e obtained from this PES agrees well with recent experimental values. Problems in the normal mode assignment of highly excited vibrational states are discussed.

Theoretical estimates of the two-stage stimulated Raman scattering (SRS) in the atmosphere had been carried out. The first stage nonlinear parametric processes are stipulated by vibration SRS of laser beam on molecules of two (e.a., nitrogen and oxygen) gases. For considered conditions the secondary SRS can be generated by two-atomic molecules such as Cl₂, F₂, H₂, N₂. The carried out analysis of two-stage SRS had shown that it can appear in the atmosphere on distances about 1 km. The calculations show that if two-stage SRS takes place, the second stage appears very sharply. This causes very essential redistribution of energies of the secondary waves and quick exhaustion of energy of laser wave.

The present work is part of a comprehensive effort engaged with the analyses of the line positions of the isotopic species '2CH4 (Hilico et a]. - J. Mo]. Spectrosc. 168, 455 1994), '3CH4 (Jouvard et a]. - J. Mo]. Spectrosc. 150, 201 - 1991) and the recent global study of '2CH3D (Nikitin et a]. -Mo]. Struct. in press - 1999). The first global analysis of the intensities of the Pentad band system of methane '2CH4 (Lu, 113, 2v2, v2+v4 and 2v4) in the 3 to 5 imregion was published in 1983 by Pierre et a]. (J. Mo]. Spectrosc. 102, 344 - 1983) This study used line positions recorded with the FTS at Orsay (Guelachvili - Nouv. Rev. Opt. App]. 3, 31 7 - 1972) and intensity data taken from the AFGL compilation (Rothman - App]. Opt. 20, 791 - 1981). The reported rms was 12%. The experimental intensities were laser measurements of Dang-Nhu et a]. (J. IVIo]. Spectrosc. 77, 57- 1979) for the strongest allowed lines of 113combined with mainly grating data from Toth et a]. (App]. Opt. 20, 932 - 1981) for the weaker transitions. The same data were exploited again in a new analysis of the Pentad of methane published in 1994 by Hilico et a]. . The use of an improved theoretical model yielded an rrns of 8% and confirmed the need for more precise intensity measurements. Series of Fourier transform spectra were recorded at Kitt Peak National Observatory under various optical densities. These new data were combined in a simultaneous fit with measurements from laser spectrometry already reported in the literature (Pine -J. Opt. Soc. Am. 66, 97 1976 ; Dang-Nhu et a]. - 1979 ; Pine - J. Chem. Phys. 97, 773 - 1992 ; Pine - J.Q.S.R.T. 57, 157- 1997).

Values of the binary absorption coefficient (mu) ₁₂ are obtained in the region of the Herzberg III band of oxygen (220 - 270 nm) for the mixture of oxygen with argon in gas phase for the temperature interval 160 - 295 K and in liquid phase--for T equals 141 K. The values of (mu) ₁₂ are found to remain constant to within 10% in the whole temperature range studied. The absence of the temperature dependence of the binary absorption coefficient (mu) ₁₂ gives evidence that induced absorption of the mixture, governed by it, is determined by absorption of a collision complex O₂ - Ar, which molecules are separated by a distance, comparable with the diameters of molecules.

Interhalogens XF₃ and XF₅ (X equals Cl,Br) are widely used for reprocessing of nuclear materials, in electronic and iron-and-steel industries. At the same time XF₃ and XF₅ may be regarded among most dangerous components in the plumes of emergency ejections of these manufactures. The Cl and Br fluorides interact actively with atmospheric gases resulting in the formation of hydrogen halogen, Cl and Br oxyfluorides and oxides which are transformed into stable complexes (HHal)_x...(H₂O)_y, where Hal equals F, Cl, Br; x + y >= 2. A study into reaction mechanisms with a participation of the XF₃ and XF₅ compounds, their secondary compounds and the applicability of the remote laser control techniques requires comprehensive information on vibration spectra of interhalogens.

Low frequency modulated N₂O hollow cathode discharges have been studied using time-resolved FTIR absorption and emission spectroscopy. Some experimental absorption data corresponding to slow transients of the discharge, as well as the temporal behavior of the different bands observed in the emission spectra, are presented here. A general exposition of the chemical reactions included in the kinetic model that explain with a satisfactory agreement that experimental stationary and time-resolved data is also given.

About 720 transitions of CF₃CFH₂ molecule in the excited 3v₁₈, v₁₁ + v₁₈, and v₁₇ states were measured in the frequency range between 49 and 142 GHz. Rotational and centrifugal distortion constants were derived from experimental spectra using Watson type Hamiltonian in the I^r representation.

The spectroscopic exhibitions of the structural non-rigidity effects in the series of the complex molecular systems with a few large amplitude motions are investigated with the application of the combination of original experimental and theoretical approaches which were tested by us earlier for the study of the floppy molecules. The characteristic times of intramolecular rearrangements are estimated for the fluorocontaining compounds having the most structural non- rigidity among the R₂NPX₂ (R equals Me, Et; X equals F, Cl, Br) systems. Using ab initio calculations of the potential energy surfaces, the tendency of the MeOPX₂ (X equals F, Cl) molecules is revealed with respect to two kinds of the large amplitude motions. They are internal rotations of the CH₃ group around the C-O bond and rotations of the CH₃ and PX₂ groups relative to the P-O bond. On the basis of the nonempirical dynamic calculations, the features of the vibrational spectrum of the MeSiF₃ molecule are studied for the region of the torsion vibrations of the CH₃ and SiF₃ groups around the C- Si bond.

The differential atomic absorption spectroscopy method is widely used both in scientific investigations and analytical applications. Absorption coefficient (absorption cross section) is an individual characteristics of every element therefore it provides for a high selectivity of an analysis. Differential absorption technique allows one to increase the selectivity by means of background absorption correction. In the cases where we should analyze gas mixtures at different pressures, we should take into account an influence of pressure on absorption line contour of the component to be analyzed. In the paper we present an estimation of such an influence. As an example, we consider an influence of pressure of analyzed gas mixture on sensitivity of RGA-11 differential atomic absorption analyzer with Zeeman background correction. This analyzer had been developed at Institute of Optical Monitoring SB RAS. The authors of the report are well experienced in its exploitation under different conditions.

The report presents the results of the study of the intramolecular V-R Coriolis interaction between closely- spaced energy levels of a molecule with a certain symmetry of the wave functions corresponding to these levels using the anthracene molecule. As an example, the consideration of V-R interactions has been shown to result in the formation of doublet structure of the 390 cm^-3 quasi-line in the emission spectrum.

The IR absorption spectra of solutions of SF₆ (natural isotopic abundance, concentration range C equals (2 - 9.5) * 10¹⁹ molecule/cm³) in liquid O₂ (temperature range /80 - 130/K, density range /2.3 - 1.7/ * 10²² molecule/cm³) were studied in the v₁ + v₃ spectral interval.

The main purpose of this study is to report measurements of H₂¹⁶O line positions at the temperature of 1300 K in 1.06 micrometers region. The H₂O frequency measurements were used to obtain values of rotational energy levels for the (111) and (012) vibrational states for J < 18.

The design of laser spectrophotometer with narrow-line tunable alexandrite laser and 30-m multipath gas cell is described. This spectrophotometer was applied to study the nonselective absorption of H₂O vapor within 0.72 - 0.78 micrometers range. The measured value of nonselective absorption coefficient was found to be equal of approximately equals 3 (DOT) 10^-8 cm^-1.

Comparison of the experimental1 and theoretical results2 for the collision induced lineshift values in rotational spectra of HF in Ar gas has shown that there is a great systematic difference between these data at higher J values. The theoretical shifts are negative and tend to zero, whereas the experimental ones become positive and increase with line number. Since the lineshift data ofRef. 1 were obtained at rather high density ofAr, we have studied the HF-Ar spectra at lower pressures from 1 to 30 bars to exclude the possible non-linear dependence on gas density.

The spectra of CH₄-He mixtures were measured in the P- and R-region of v₃ vibration-rotation band at lower pressures of 0.26 - 1.0 bar and for the whole band at higher pressures up to 90 bar. The broadening line coefficients were found from lower pressure data for the lines of P branch. These coefficients were calculated in the frame of the semi-classical approach. They agree with the experimental values, but a small J-dependent deviation was observed. The line mixing effect was observed. At higher pressure it was interpreted in the terms of the adjusted branch-coupling model. At lower pressure the line mixing effect was found to be especially pronounced in the region of relatively weak lines forming the clusters R(16) - R(19).

In the given paper the correct model for intermolecular potential is proposed. The model takes into account the vibrational dependence of inter- and intra-molecular distances. To create the model the Lennard-Jones atom-atomic potentials are used. In the framework of our model the Talor expansion is applied for vibrational coordinates. Isotropic terms of intermolecular potential are only taken into account. As a result the correct expressions for intermolecular potential of HF-Ar colliding system is found. The contribution of vibrational dependence into the line shift was estimated. Thus, the vibrational corrections for Robert-Bonamy formalism are obtained. Our model allows one to calculate most exactly the line shifts in near infrared and visible ranges.

A new spectroscopic effect of strong self-action was observed for the first time in molecular gases for vibrational transitions to combined states, in which the strongly IR active v₃ mode is involved. Transformations of the v₃, v₁ + v₃, v₂ + v₄ band shapes of ³²SF₆, ³⁴SF₆, ¹²CF₄, ¹³CF₄, ¹⁴NF₃ upon variation of density (T equals 293 K) were studied for pure gas (p < 70 Amagat) and its dilute mixtures with Ar, Kr, Xe (p_mixt < 150 Amagat). A strong linear dependence of the second spectral moment M₂ on density for v₃ and v₁ + v₃ bands in pure gases was observed, whereas no effect was found in dilute mixtures and for v₂ + v₄ band in pure gases.

Temperature dependence of ultrasound and hypersound velocity close to singular point in acetone-water solution was studied. The method of simultaneous registration of Mandelshtam-Brillouin components on essentially different angles of light scattering allows to observe the negative dispersion of high-frequency sound.

An algebraic approximation for a line halfwidth at the half- maximum ((delta) ) was obtained from the calculated values of (delta) , which depends on the collision broadening and narrowing parameters and the Doppler halfwidth. Both the hard and soft collision models describing the effect of velocity-changing collisions were approximated. The mean discrepancy between the approximated and exact values of (delta) does not exceed 0.1 divided by 0.15%. A simple criterion was developed which allows one to judge about the correspondence of the experimental dependence of (delta) on buffer gas pressure to hard or soft collision model.

We measured a series of absorption profiles of the v₃ band of CH₃F perturbed by helium. The measurements were performed at room temperature for helium pressures from 1 to 90 atm. We observe significant deviations of measured profiles with respect to those calculated as a sum of lines having Lorentzian shapes. To interpret the observed deviations, we consider various models of line mixing. The calculations performed in the ECS approximation provide the most reasonable agreement with the measured band shapes reproducing the existing data on line broadening coefficients within the limits of experimental uncertainty. Special attention is paid to the analysis of the differences of interbranch and intrabranch line mixing, that is to the structure of relaxation matrix.

Sum and difference frequency generators of Er³⁺:CaF₂ ((lambda) equals 2.76 micrometers ), Er³⁺:YAG ((lambda) equals 2.94 micrometers ), and cw CO₂ lasers with ZnGeP₂ and CdSe single crystals has been developed to enlarge the possibilities of spectroscopic systems based on CO₂ lasers. The generated spectra overlapped the ranges from 2.1 to 2.3 and from 3.7 to 4.3 micrometers which coincide with the two main atmosphere transparency windows. The energy effectiveness of sum frequency generation with 4.5 mm ZnGeP₂ crystal realized is about 3% at phase-matching angle of 52 degree(s) and 12% for difference frequency generation in 40-mm CdSe crystals at phase-matching angle of 72 degree(s)40'. The latter source, in particular, may be used in CH₄ lidar.

In the present work the algebraic method of modeling of internal vibrational coordinates for excited vibrational transitions is proposed. Within the framework of this method, the internal vibrational coordinates are presented as polylinear forms, which depend on the corresponding powers of normal coordinates. The coefficients in these polylinear forms are the sought-for elements of higher-order tensors for valent and deformation vibrations of spherical- symmetry molecules. Using the formulae obtained, the calculations of coefficients L_i^rs, L_i^rst, L_i^rstk have been performed for the molecules of methane CH₄ and deutero-substituted methane CD₄.

Laser setup for mobile long-range DIAL lidar is developed in the Institute of Laser Physics (Novosibirsk, Russia). It includes two tunable pulse-periodic TEA CO₂ lasers operated on 85 emission lines. Energy and peak power of a laser pulses exceed 10 J and 100 MW accordingly. Width of laser pulses is 30 ns. The lasers emit a pair of optical pulses on different wavelengths in a spectral range of 9.15 - 10.86 micrometers with pulse repetition frequency of 0.1 - 2 Hz and temporary delay between pulses of 0.2 - 3 ms. The laser emission is multimode and its polarization is linear. The estimations of developed lidar monitoring range for various mode of operation are carried out. Lidar can be mounted inside of mini-bus. The dimensions of lidar frame is 2250 X 840 X 1500 mm, total weight is approximately 600 kg, electrical consumption is about 2 kVA (220 VAC/50 (60) Hz).

An essential improvement of automated high-precision millimeter-wave spectrometer is described. In order to investigate lineshapes a multimode frequency modulation of radiation source is realized. Matching of quasioptic absorbing cell with radiation source and detector was improved to reduce well-known problem of standing waves. PLL systems were essentially improved that allowed us to realize survey mode of spectrometer operation. For the frequency step about 50 kHz the speed of survey spectra recording is about 10 GHz per hour (using the synthesizer-based mode). The whole frequency range of the spectrometer is 48 - 148 GHz.

A high resolution and high sensitivity spectroscopic technique is developed by utilizing a Bruker IFS 120HR Fourier-transform spectrometer to detect the absorption spectra of samples inside a Ti:Sapphire laser cavity. A trigger-sampling system makes it possible to investigate the evolution of intra-cavity laser absorption spectra with the generation time. Owing to the multiplex advantage of FTS, the quantum noise in ICLAS can be significantly reduced in FT-ICLAS. The absorption of atmospheric water vapor in the range of 12450 - 12700 cm^-1 was recorded at a resolution of 0.05 cm^-1 to examine the performance of our FT-ICLAS apparatus. With 200 scans on the FT-ICLAS within 2 hours, a sensitivity of 10^-9 cm^-1 was obtained. It is also demonstrated that the FT-ICLAS is able to record both positions and intensities in a wide spectral range. This technique was applied to measure the HOD v_OD equals 5 overtone in the range of 12550 - 12900 cm^-1 with a resolution of 0.05 cm^-1. The spectrum was analyzed with the ground states combination differences method and the spectroscopic parameters were obtained. For 81.1% rotational levels in this band, the difference between calculate and experimental energy was less than 0.01 cm^-1 which indicated that both the recording and analyzing of this spectrum were successful.

Phase-matched difference-mixing of the frequency tunable CO₂ lasers in three nonlinear crystals is considered to generate a tunable submillimeter radiation. Optical properties of ZnGeP₂, AgGaSe₂, and new promising nonlinear mixed crystals like AgGa_xIn_1-xSe₂ in middle IR and FIR spectral ranges have been investigated. The coefficients of Sellmeier dispersion equations for AgGa_xIn_1-xSe₂ and AgGaSe₂ for IR and those for ZnGeP₂ for FIR have been determined. Phase- matching curves and phase-matching angular widths for both direct and backward waves have been calculated. A principle possibility of application of the emission converted is shown to control some atmospheric pollutants.

The RELIP (Retrieving Line Parameters) software for photo- acoustic (PA)-spectroscopy data processing is developed in the Laboratory of Atmospheric Absorption Spectroscopy of the Institute of Atmospheric Optics SB RAS. This software is developed for reconstruction of line centers and halfwidths from experimental absorption spectra. The well-known line contours such as Doppler, Voigt, and Lorentz shapes are used in the fitting procedure. It is possible to reconstruct simultaneously the above-mentioned parameters for several absorption lines. The experimental data of a special form such as frequency derivative of the PA signal are acceptable. There is an additional option aimed to compensate for the background of a signal. The software provides the graphical presentation of the measurement data and fitting results together with the tables. There are many options simplifying processing of experimental and model data using this software. The experimental data on the PA signal and the PA signal derivative for the absorption bands of H₂O lying near 0.69 micrometers and 0.59 micrometers as well as the model calculations are used at the software testing.

A basis set of algorithms for various tasks of greenhouse gases monitoring in the Earth's atmosphere has recently developed and built into first version of user-friendly software FIRE-ARMS. This software includes both algorithms for forward spectra simulation for the cases of up-looking and down-looking observations and algorithms for retrieval of pressure, temperature, atmospheric constituents concentrations profiles. Presented in this paper, study is devoted to subsequent development of combined techniques for the monitoring of greenhouse gases and further improvements of FIRE-ARMS as a useful tool for researchers working in the field of Global Change monitoring. All retrieval algorithms developed and built into the last version of FIRE-ARMS are presented. The technique of detection of spectral features belonging to isotopic species in radiance spectra of atmosphere is presented. This technique is illustrated by HDO/H₂O ratio determination from IMG spectra.

This paper presents the recently developed information content diffusion facilities, e.g. the WWW-server of GEISA, MS DOS, WINDOWS-95/NT, and UNIX software packages, associated with the 1997 version of the GEISA-(Gestion et Etude des Informations Spectroscopiques Atmospheriques; word translation: Management and Study of Atmospheric Spectroscopic Information) infrared spectroscopic databank developed at LMD (Laboratoire de Meteorologie Dynamique, France). GEISA-97 individual lines file involves 42 molecules (96 isotopic species) and contains 1,346,266 entries, between 0 and 22,656 cm^-1. GEISA-97 also has a catalog of cross-sections at different temperatures and pressures for species (such as chlorofluorocarbons) with complex spectra. The current version of the GEISA-97 cross- section databank contains 4,716,743 entries related to 23 molecules between 555 and 1700 cm^-1.

We present estimates of influence of refraction on gas throws concentration measure by trace gas analyzer. The used model of spatial distribution of gas concentrations is correspond to gas throws from pipe lines. The molecules of CH₄ were considered as markers of such gas throw. Influence of refraction on parameters of collimated probing beam was shown to result mainly to its shift relatively receiver telescope.

Investigation of gas media spectroscopy at high temperature is accompanied by large and complex data amount. In order to manage these data one should use specialized information systems able to execute formal stale operations with friendly interface. In the present paper we discuss the problems of development of an integral distributed information system using up-to-date object oriented technologies and technologies for distributed systems based on CORBA 2.0 (Common Object Request Broker Architecture). On the basis of modern information technologies we have developed HOTGAS and SMOLA software. Both can be run under Windows operation system. HOTGAS is intended for calculation of spectral line parameters (SLP) and absorption coefficients for CO, CO₂ and H₂O in 250 - 3000 K temperature range. SMOLA is intended for accumulation, systematization and use of published SLP data for different molecules. It also has a graphic interface and possesses the advantages of other Windows software. To provide comprehensive informational support and to execute all the diversity of tasks in the sphere of rovibrational spectroscopy of gas media we offer a project for integral distributed informational system design.

The recent in situ experiment by Vogelmann et al devoted to studies of the excess absorption to be for the clear humid atmosphere within the 0.94 micrometers water band in the visible region shows that the problem of the absorption enhancement is caused rather by the uncounted molecular absorption into bands than by an aerosol absorption. On the other hand, our recent studies of the nonlinear continuum absorption of the pure water vapor had described the continuum absorption of the pure water vapor in the MW and IR. It is interesting to apply the nonlinear continuum, that is followed from the fundamental properties of the hypothetical absorption scattering interaction, to account for the absorption in the near IR region such as the band of 10400 - 10900 cm^-1. The observed enhancement of 5 - 10% in comparison with a method using the Lorentzian is calculated and this is a result of the influence of UV bands of nitrogen on the selective continuum of the pure water. In a whole, the approach developed earlier has been successfully extended to the foreign broadening case.

Some models of an atmosphere are considered. In view of these models the account of intensity direct solar UV radiation on a surface of the Earth is executed. The variability of intensity of flows UV radiation is investigated depending on various thermodynamic and aerosol models, total ozone abundance and its vertical structure, height of the Sun.