Detailed studies of physical and chemical conditions in regions of star formation need multiline observations of different molecular species. A correct retrieval of systematic velocity fields in these objects from such measurements requires accuracy of rest frequencies of about 1 m/s. Because of a very small thermal line broadening at typical kinetic temperatures in dark clouds (Tk ~10 K) the precise knowledge of the hyperfine structure of observed transitions is extremely important for line shape analysis. Unfortunately, the available laboratory uncertainty for a large number of measured transitions is about 30 - 100 kHz. This value is comparable with molecular line widths in dark clouds and very often it is sufficient only for identification of observed species but not for detailed kinematical studies from multiline data. Taking into account our recent laboratory and radio astronomical studies, a large set of molecular spectra were measured with ~10^-9 relative uncertainty, including precise estimates of hf structure. It is shown that whereas laboratory methods are sufficiently good for stable molecules, the use of radio astronomical measurements may be preferable for laboratory unstable species.

Five high resolution water line lists HITEMP, SCAN, AMES, TOMSK, and BT2 available from the literature were used to simulate medium and low resolution observed spectra in the 600-8000 cm^-1 spectral interval for temperatures 1550 and 2900 K. The simulation shows that there is no a line list which is uniformly better than the others. However, in general, the BT2 line list is the most accurate whereas the SCAN line list is the least accurate.

Here we report a systematic theoretical investigation of the vibrational spectra of bare gold clusters Au_n (from n=3 to n=20) and oxidized gold clusters Au₂₀0, Au₂₀0₂. Density Functional Theory (DFT) and SBK basis set (for the effective core potential with relativistic correction) was used to calculate the structure and vibrational frequencies of gold clusters. A weak correlation between pattern of Au_n spectrum (10-200 cm^-1 range) and their structure was found. Calculated IR spectra of Au₂₀0 and Au₂₀0₂ complexes are strong depend from the their structure and types of 0-Au bonds and can be used for the identification of the structures of oxidized gold clusters.

Thanks to the record ofnew FTS spectra of O₃ in the 4300 cm¹ region, the 122-000 band is now observed. Assignments of line transitions for following values of rotational quantum numbers J and K_a: 10 < J < 51 , K_a ≤ 8 were done. In the linelist about 443 transitions of v₁+2v₂+2v₃ band are presented. To correctly reproduce the obtained energy levels of (122) state, the very weak "dark state" (400) was introduced. A data reduction has been done using effective Hamiltonian for three interacting states {400, 122 023}, which are coupled through the usual Coriolis and high order rotational and vibrational resonances. The final fit on the 589 energy levels is quite satisfactory. The root mean square deviation between observed and calculated values is about O.0029cm^-1. The fit of line intensities allows us to derived transition moment parameters for 2v₂+3v₃ and v₁+2v₂+2v₃ bands.

The microwave rotational spectra of parent and five isotopic species with ¹³C and ¹⁸0 in natural abundance for 2- methyl-1,3-dioxane, C₅H₁₀0₂, have been observed in the 28.0 - 44.0 GHz frequency region. The a - and c - type transitions with 4 ≤ J ≤ 10 have been assigned. The rotational constants for all isotopomers were determined. The substituted coordinates of the heavy atoms were calculated from the principal moments of inertia of normal and ¹³C(2)¹²C₄H₁₀¹⁶0₂, ¹³C(4)¹²C₄H₁₀¹⁶0₂, ¹³C(5)¹²C₄H₁₀¹⁶0₂, ¹³C(7)¹²C₄H₁₀¹⁶0, C₅H₁₀¹⁶0¹⁸0 isotopomers using Kraitchman's equations. Partial substituted r_s structure of 2-methyl-1,3-dioxane molecule has been determined.

The rotational spectrum of 4-methyl-1,3-dioxane, C₅H₁₀0₂, has been recorded from 16.0 to 40.0 GHz. The a-, b- and C- type transitions with J≤57 have been observed and assigned for the normal species in the ground vibrational state. The rotational constants and the quartic centrifugal distortion constants were determined to be A = 4802.335(2) MHz, B = 2376.163(1) MHz, C = 1738.852(1) MHz and Δ_J = 0.1496(6) kHz, Δ_JK = 0.157(5) kHz, Δ_K = 0.76(3) kHz, δJ = 0.0423(1) kHz, δK 0.260(3) kHz. Stark effect measurements were used to determine the projections of the dipole moment on the principal inertial axes (in Debye units): μ_a = 0.73(1), μ_b = 1.32(1), _c = 1.36(1) and μ_tot = 2.03(2). Comparison of the experimental rotational constants and dipole moment components with results of ab initio calculations (B3PW91/aug-cc-pVDZ) shown that 4-methyl-l,3-dioxane exist in chair form with equatorial orientation of methyl group.

Using the effective Hamiltonian approach the global least-squares fittings of the vibration-rotation line positions of three rare isotopic species ¹⁵N¹⁵N¹⁶O, ¹⁴N¹⁴N¹⁷O, and ¹⁴N¹⁴N¹⁸O of nitrous oxide molecules have been performed. The set of the input data consists of Microwave, Fourier Transform and CRDS line positions which lie in the spectral range 0-6800 cm^-1. The fitted sets of the effective Hamiltonian parameters reproduce the experimental line positions with the accuracies close to the experimental uncertainties.

This study is the continuation of our analysis of emission spectra of pure D₂0. The spectra have been recorded in the 320 - 860 and 1750 - 4300 cm^-1 spectral regions at different pressures and temperatures. The measurements were performed in an alumina cell with an effective length of hot gas of about 50 cm. All spectra have been recorded by using the Bruker IFS 120 spectrometer at the Physikalisch-Chemisches-Institut, Justus-Liebig-Universitat Giessen (Germany). More than 5600 lines have been assigned to the second triad {(030), (110), (011)} of interacting states of the D₂¹⁶0 molecule. These transitions were assigned to 24 vibration-rotation and rotational bands. An extended set of more than 1500 experimental rovibrational levels for the (030), (110), and (011) interacting states has been obtained. The maximum values of rotational quantum numbers are J_max = 30 and K_{a max} = 21 with E_max = 10568 cm^-1 for the (011) state; J_max = 29 and K_{a max} = 21 with E_max= 10540 cm^-1 for the (030) state, and Jm 26 and Ka max 22 with Eniax 10488 cm1 for the (110) state. A comparison of the observed energy levels with the best available values from literature and with the global prediction is discussed.

The first version of the expert system for working with large molecular vibration-rotation spectra is developed. The spectra are regarded as sets of elements - spectral lines having some characteristics. The last may be line positions, strengths or broadening parameters. The expert system is capable to find the units, intersections, and relative complement; these operations are frequently used in spectra processing. In all these operations, which are standard operations of theory of sets, the comparison of lines in two spectra is performing using pattern recognition algorithms.

Experimental investigations of absorption and emission spectra of the water vapor at high temperature (1800....3000K) are recorded in the region 2000 - 12000 cm^-1. Hot water vapour was produced by a Multyplaz-2500 plasma source at atmospheric pressure. Highly sensitive Intracavity laser spectrometer was used to study weak absorption spectra in around 9400 cm^-1. Emission spectra of the flame were recorded in the region 2000. ..6000 cm^-1 using the IFS-125HR Fourier transform spectrometer with spectral resolution of 0.03 cm^-1 and between 9500 and 12000 cm^-1 using the DFS-452 grating spectrometer with spectral resolution of 0.13 cm^-1. The spectra are very dense over the entire wave number regions investigated, showing in addition to water lines emission of OH and other molecules.

On the basis of the analysis of influence of isotope substitution on system of the electronic and nuclear equations for any molecular system conditions of invariance are formulated relatively to the isotope substitution surfaces of the potential energy expressed in the Cartesian coordinates. Except for that it is shown, that this property of potential function is the consequence of the appropriate property of this function expressed in curvilinear internal coordinates, that, in its turn, allows at theoretical research of vibration - rotation spectra of isotope substituted molecules, and also at the solution of a direct and the inverse anharmonic problems to avoid the use of curvilinear internal coordinates, having replaced them by Cartesian.

Some new applications of so-called Rotational Energy Surface (RES) are discussed. As shown before, the method allows to discover some important qualitative features in rovibrational spectra of triatomics - e.g., energy level clustering. While trying to generalize the results, we developed a universal numerical procedure, allowing, particularly, to predict the formation of 6-fold energy clusters in spectra of PH₃ by quasiclassical means.

Recent accurate observations [1] of collision-induced absorption (CIA) in the nitrogen and oxygen fundamentals pointed at the existence of the minimum in its integrated intensity temperature variation. This work aims at simulation of the CIA intensity in N₂ using quantum chemical complete potential energy and dipole surfaces for N₂-N₂ system. The absolute magnitude of CIA intensity was found to be fairly sensitive to the level of ab initio calculations, in particular to the quality of the basis set. The presence of the minimum on the integrated CIA temperature dependence was shown irrespective to the basis set, though its position is subject to notable variations. The capability of ab initio methods to correctly predict the CIA intensity in weakly interacting systems is clearly demonstrated.

The Effective Hamiltonian method uses the perturbation expansions and the problem of series convergence are important. It was shown that poor convergence is typically observing for high-J levels and highly excited vibrational states. Several methods of resummation have been proposed, Pade and Borel methods, multivalued quadratic approximants, generating functions, Euler method. In this report the Euler series transformation is applied to summation of divergent series within the EH method. The calculations were performed for H₂, H₃ ⁺, H₂0 molecules.

The paper is aimed at the creation of the model allowing one to calculate the relaxation parameters caused by the transitions into highly excited vibrational states of CO molecule. Halfwidth and lineshift calculations are made in the framework of semiclassical impact theory. Intermolecular potential includes dipole-dipole, dipole-quadrupole, quadrupole-quadrupole and isotropic part of polarization interactions. The feature of this model is the development of traditional calculations into the highly lying vibrational states of CO molecule. To make this the necessary matrix elements of dipole, quadrupole moments, polarizability are numerically defined using semiempirical and ab initio functions. Intramolecular potential function was defined as Morse potential fitted to ab initio energy data.

The IR absorption spectra of CHF₃ in mixtures with He, Ar and N₂ were recorded in the region of 400-800 cm^-1 using the Bruker IFS-28 Fourier transform spectrometer at resolution of 0.6 cm^-1. The shapes of the parallel v₃(A₁) and perpendicular v₆(E) bands were studied at perturbing gas pressure range of 25-100 atm. The observed behavior of the shapes for these two bands at the pressure increase is similar. The Q-branch widths increase at the pressure rise for all pertubers, but the slopes are quite different from those for individual lines. The Q-branch broadening for He mixture is much smaller than that for Ar mixture (for individual lines these values are close). To the contrary, the Q-branch broadening for Ar and N₂ mixtures is similar whereas for the lines these values are different. The Hermann-Wallis factor was introduced to describe the line intensity distribution in P and R branches. The shape calculations were performed in the approximation of Lorentzian lines sum. At higher pressures the calculated shapes are totally different from the experimental ones. We attributed this difference to line mixing effect. We used the adjusted branch coupling model in shape calculations to estimate this effect on the observed shapes. The results of the calculations explain qualitatively the observed band shape transformations.

Halfwidths and lineshifts of water vapour by Ar pressure were calculated in the framework of semiclassical broadening theory. Anisotropic and isotropic parts of polarization interactions are taken into account, when relaxation parameters are calculated. H₂0 mean polarizability in 301 vibrational state was determined earlier using the measured linesfifts. H₂0 polarizability z-component in 301 vibrational state was determined using the measured lineshifts in this work at the first time. The calculated relaxation parameters were in a good agreement with the measured one. Halfwidths and lineshifts temperature dependence is calculated within the interval 100-800 K.

Intermolecular interaction potential appears to be a value which performs the relationship between divisions of physics seemingly far from each other. Accurate consideration of the quantum problem of interacting molecules allows one to refine the employment of theoretical expressions for the potential describing one or other type ofprocesses. Thus, the potential which can be named classical one is common for the absorption coefficient in the line wing and for the second virial coefficient. This fact provides a possibility of using the temperature dependent classical potential obtained from the line wing absorption coefficient data for the calculation of the second virial coefficient. The use of the line wing absorption coefficient following from the line wing theory, which is appreciably defined by the behaviour of the classical intermolecular interaction potential, leads to noticeable changes in the cooling rates at large heights in some spectral regions.

Perturbation theory and representation of interruption function as the power series of interaction strength are widely used in the frame of the impact approximation. When the impact parameters are small, the intermolecular interaction becomes strong and the divergence of perturbation series should be expected [1]. This problem has become the main goal of many previous studies (see, for instance, [2, 3] and references therein) and several approaches were developed to overcome the perturbation series divergence. In this paper the generalized Euler transformation was used to solve the problem. The generalized Euler transformation was based on the full resonance approximation as a starting point. This approach allows one to obtain the convergent expression for the interruption function at short distances between colliding molecules, which is similar to the well known expressions of the Anderson theory.

We report the first direct investigations of vibrational dynamics in isolated polyatomic molecules by means of Raman spectroscopy. A pump-probe experimental scheme is applied where laser pumping of one mode of a molecule is followed by probing its anti-Stokes Raman spectrum, so that a decrease ofRaman signal with the probe-pump delay time tells us about intramolecular vibrational redistribution (IVR) of the energy from the initially excited mode to the other modes. Experimental results for terminal acetylene molecules are presented and discussed. The principal observation is that IVR times in our studies are much shorter than those estimated previously for the same molecules from high-resolution spectroscopy ofthe cold molecular beams. We analyze this difference assuming that the rotational degrees of freedom, which are highly populated in our case of gas at room temperature, play an important role in mediating IVR in the molecules under consideration.

A special shape of modulation of laser diode injection current is provided when the frequency modulation is not accompanied with amplitude modulation. Such approach permits to suppress essentially the influence of laser emission instabilities. When being applied to gas analysis it gives the possibility of long-term remote components monitoring. The stable relative absorptions of 8xl0^-7 without special calibration are demonstrated. In combination with multipass cell (50 cm between the mirrors, 90 m optical length) it gives the absorption coefficient of l.2x10^-10cm^-1. As an example the daily evolution of atmosphere NO₂ admixtures have been measured with a precision of O.5ppb.

A cavity ring-down spectroscopy with off-axis multipass cell and space separated detectors is suggested to record absorption spectrum without modulation of the diode laser intensity. The spectral resolution is ~0.0003 cm^-1. The whole spectrum is obtained for a one continuous tuning of the laser frequency for ~20 ms. Apart from conventional CRDS a really needed rise time of the detectors are 1000 times slower. The recording of the whole spectrum for a one measurement give an additional possibilities of signal extraction at relatively high noise. The technique is applied to absorption measurement of NO2 in atmosphere.

The middle IR or so-called "fingerprint" region of atmospheric gases is most attractive for multicomponent remote gas analysis of the atmosphere. Femtosecond lidars can be applied to this purpose. In recent years compact powerful laser systems have been developed, which emit the pulses of femtosecond duration. First of all, those are solid-state lasers based on wide-band active media: Ti³⁺:Al₂0₃ (λ = 0.75-1 μm) and Cr³⁺:MgSiO₄ (1.2-1.32 μm). Frequency conversion of these quite promising and basic sources of super-short pulses into other spectral ranges using non-centrosymmetrical nonlinear crystals seems to be quite attractive, especially if preserving duration of the transformed radiation. Usually to overcome the problem middle IR femtosecond pulses are generating with two- or three-stage low efficiency frequency converters with nonlinear crystals. High efficiency middle IR semiconductor crystals are not suitable for one-stage generation because high optical loss at near IR. This study was aimed at search and investigation of nonlinear crystals, in which effective single-stage optical parametric oscillators. The investigation includes estimation of phase- and group-velocity matching conditions, phase-matching spectral and angular widths, and potential efficiencies. The possibilities of using a hyper broadband nonlinear-optical frequency converter of femtosecond pulse radiation for design of multicomponent mixture analyzers are investigated. The method of broadband lidar sensing of atmospheric gases by the DOAS-technique (Differential Optical Absorption Spectroscopy) is described. The numerical simulation of DOAS sensing of atmospheric gas components using the frequency-converted femtosecond radiation is carried out.

There are about 600 volatile compounds in air expired by man, including molecules-biomarkers of endogenous (produced in organism) origin, the specificity of generation and excretion mechanisms of which is sufficient for studies of both normal and pathologic processes. The goal of this work is analysis of the human-expired air by means of the intracavity laser photoacoustic sensor intended for detection of air gas admixtures having the absorption bands in the wavelength spectral range 9.2 - 10.8 μm. The sensor principle of operation is based on the photoacoustic effect caused by gas absorption of the CO₂ laser radiation. Measurements were conducted with a test group consisting of 100 persons and a group of patients (60 persons) affected by different bronchopulnionary pathologies. The state of health of each group members was determined from questioning data. The spectral absorption dependences were normalized to referent points and then investigated in respect to a qualitative coincidence. The typical results are presented below.

Specifications and examples of application of laser gas-analyzers of near- and mid-infrared ranges for diagnostics of greenhouse gases (C0₂, C₂H₄, and CH₄) emission by vegetation biosystems both under standard conditions and under impacts of natural and anthropogenic stresses are considered in the report. The gas-analyzer complex includes: 1) gas-analyzer with a multipass absorption cell based on the frequency-tunable diode laser (1600-1 650 nm) for measuring sub-background methane concentrations (≤20 ppbV); 2) gas-analyzer based on the wave-guide C0₂-laser equipped with the intracavity acoustic detector capable of fast frequency scanning in the 9 and 10 μm generation bands and having the ethylene-sensitivity better than 1 ppbV. The technology of measurements of gas emission by plant stripped leaves and coniferous needles is described and the measurements of CO₂ and CH₄ emissions are presented.

In the work an analysis of possible errors of the longwave radiative fluxes calculation due to spectroscopic uncertainties of HITRAN2004 database lines parameters and continuum models is carried out. Upper estimations of the fluxes calculation errors are founded. The errors are 0.2% for downward and 0.25% for upward fluxes. It is shown that the uncertainties of water vapor continual absorption may cause the fluxes error more then 1%, that exceeds the line parameters error. A comparison of the radiative fluxes calculated with different continuum models used in radiative codes is made.

Multilayer perceptron (MLP) as universal approximator may be used for fast retrieval of atmospheric parameters such as vertical profiles of temperature, humidity and concentration of absorbing gases from high-resolution infrared spectra measured by satellite sensors. On the one hand, the number of spectral channels even necessary for retrieval of particular atmospheric parameter is very high, so practical use of MLP needs for effective compression of spectral data with tolerable loss of accuracy. On the other hand, algorithm of error back propagation becomes more effective if the input data vector contains uncorrelated values with zero means, their covariance are approximately equal, and information content of training set is maximized. The modified method of principal components (or empirical orthogonal functions expansion) satisfies to all above requirements. The MLP may be constructed using relevant truncated vectors of principal components as input and output data. Such MLP has fewer dimensions (the number of input, output and hidden neurons) and requires less time for training than MLP using the high-resolution spectrum as input vector and set of vertical profiles of atmospheric parameters as output vector. The developed technique was applied to AIRS observations to retrieve temperature, humidity and methane content. The empirical orthogonal functions were obtained as eigenvectors of matrix G = S_e^-1/2S_RS_e^-1/2, where S_R is sample covariance matrix built on real AIRS measurements over given region, and S_e is error covariance matrix characterizing the sensor. The set of measured and model profiles as well as surface temperature and pressure were used for construction of empirical orthogonal functions to represent output data of MLP as truncated expansion. Error profiles and examples of temperature and methane maps are presented.

The technique which makes it possible to simultaneously determine the temperature T and the partial pressure of carbon dioxide in a vibrationally equilibrium gas mixture at atmospheric pressure by using the spectral distribution of the unsaturated absorption coefficient at the oscillation lines of a tunable CO₂ laser is presented. The results of model calculations of the influence of H₂0 molecules upon the precision of determining temperature and partial pressure of CO₂ in C0₂:N₂:H₂0=10:80: 10 mixture at full pressure 1 atm and temperature T=l000 K have given.

General regular methods of solution of ill-posed inverse problems and their application to geophysical sounding of Earth interior were developing during long time at Institute of Mathematics and Mechanics of Ural Branch of RAS. In this paper we apply the developed regular methods of solution of the inverse problems for retrieval of vertical temperature profiles from high-resolution thermal emission spectra of atmosphere observed at nadir. Synthetic spectra of sensor like 1MG have been used to test the methods in frame of computational experiments of retrieval of vertical temperature profile. These synthetic spectra were simulated for clear sky weak aerosol atmosphere with line-by-line forward model FIRE-ARMS then convoluted with 1MG instrumental line shape function, arid equivalent nose of 1MG was added. In order to retrieve vertical temperature profile within 0-70 km, we used emission spectra of atmosphere of CO₂ band in the range of 680-830 cm^-1. The computational experiments showed good convergence of all methods started from different initial guess profiles to the target T-profile (known T-profile) with average standard deviation in troposphere within 1K. Deviations of different methods are within 1.5 K. The methods were also applied to temperature retrieval from real data of VIRTEM measurements when emission spectra of the atmosphere were obtained simultaneously with measurements of temperature and humidity profiles over water surface using airplane for elevations up to 8 km. It's shown that the regular methods of solution of inverse problem allow retrieving temperature profile from down-looking high-resolution atmospheric emission spectra with acceptable accuracy even if initial guess atmospheric states are quite far from the target T-profile.

Method of laser-induced fluorescence (LIF), widely used for study of plants, showed certain promises in study of influence of ozonosphere variations on arboreous plants. Creation of fluorescent channel at the Siberian Lidar Station (SLS), in addition to the systematic measurements of total ozone content at the SLS, makes it possible to obtain fluorescence characteristics of plants, connected with photosynthetic activity. For excitation of fluorescence we use second and third harmonic radiation of Nd:YAG laser. The intensity of the detected radiation is measured at the spectral range 660 - 820 nm. A measurement technique for study not only spectral but also temporal dependence of fluorescent signals is proposed.

Reactions of ozone with CH₃Cl, CH₂Cl₂, CHCl₃, CCL₄, adsorbed on ice surface, have been investigated under temperatures 77 - 292 K. Ozonation reaction takes place only when temperature is above 210 K with formation of different chlorine oxides. The products of reaction have been identified by low temperature FTIR-spectroscopy.

The urgency of creating the information-computational systems (ICS) on molecular spectroscopy follows from the circumstance that for some molecules the number of calculated energy levels counts hundreds of thousands, and the number of spectral lines sometimes reaches hundreds of millions. Publication of such data volumes in regular journals is inappropriate. Comparison of different calculated spectral characteristics or their comparison with experimental data beyond computer processing is hopeless. We find information systems to be an adequate form for holding such data volumes and a toolkit for handling them. Correct digital data processing requires appropriate sets of metadata arranged in the form of ontology of molecular spectroscopy. Our information system provides the data on spectral line parameters, water molecule energy levels, and absorption coefficients. Within this distributed IS one can solve two types of problems: manipulation with data and calculation of spectral functions. Among the latest experimental data in the IS there are data obtained at the Institute of Applied Physics RAS. To calculate the absorption coefficients for the molecules of carbonic acid gas, we take into consideration spectral line interference.

Here we present a Principal Components (PCs) method of retrieval of the HDO/H₂O vertical profile using atmospheric radiances observed from space by sensor like IMG as well as atmospheric transmittance spectra observed by ground based FTIR. The method is based on the expansion of the retrieved profile on eigenvectors of covariance matrix of model profiles extracted from the isotopic Atmospheric General Circulation Model (AGCM). A priori information of covariance matrix compensates partially the lack of information containing in weighting functions for HDO in lower atmospheric layer (0-1 km) and layers above 10 km. Error estimation of the retrieval scheme was made using closed model computations with synthetic spectra ofIMG and known sets of T, H₂0, HDO profiles and its value is within 8% - 70% for vertical profile and not greater than l8% for columnar value of HDO/H20 ratio. The method was applied to IMG/ADEOS spectra measured over the ocean in clear sky conditions. Latitudinal distributions ofHDO/H20 profile and columnar HDO/H₂0 ratio are retrieved over Pacific Ocean for the time interval from winter of 1996 to summer of 1997. The retrieved HDO/H₂0 from IMG/ADEOS data and simulated with isotopic AGCM are in a good agreement. FTIR is Poker Flat high resolution ground based Fourier transform spectrometer for up-looking observation of atmosphere in the spectral range from 750-4300 cm^-1 with resolution 0.0019 cm^-1 and high signal to noise ratio. The spectrometer is located at the Poker Flat Research Range (Altitude 0.61km; latitude 65.11N; longitude 147.42W) of the Geophysical Institute at the University of Alaska Fairbanks. Poker Flat FTS is operating from 1999, observation modes are atmospheric emission and solar radiation absorption. The measured atmospheric traiismittances are supported by sonde observations of T and water vapour profiles. The HDO/H₂0 PCs retrieval method was also adapted for using the high spectral resolution atmospheric transmittances observed by FTIR. Linear regression of PCs of the HDO/H₂0 profiles was obtained in this case. Error estimation of the retrieval scheme was made using closed model computations with synthetic spectra ofthe FTIR and known sets of T, H₂0, HDO profiles and its value is within 6% - 67% for vertical profile but not greater than lO% for columnar value of HDO/H₂0 ratio. As an example, HDO/H₂0 vertical profiles were retrieved using a few samples of FTIR spectra observed at the Poker Flat Research Range from 2000 to 2004 and compared with isotope AGCM outputs for Alaska's atmosphere.

Recent observations of the water dimer third stretching overtone in the open atmosphere lead onto the idea to look for the signatures of partially deuterated dimers in the range of their stretching fundamentals. On the one hand, the third overtone intensity is roughly three orders of magnitude less than that in the fundamental. On the other hand, the natural abundances of the water isotopomers are known to extend below 0.2% with respect to that of the principal one. The gain can be achieved, however, because of the use of the spectral range which is less crowded by the principal water isotopologue rovibrational lines, because of significant isotopic shift of the band origin. This work is targeted at preliminary search of the suitable spectral window and other conditions which might favor the observation of partially deuterated water dimers using FTIR or tunable lasers instruments.

The Greenhouse gases Observing Satellite (GOSAT) is a Japanese satellite that is intended to observe CO₂ concentration from space and to contribute to advancement of research of the source/sink estimation of CO₂. The GOSAT main sensor is a Fourier Transform Spectrometer (FTS) named "TANSO-FTS", which covers a wide terrestrial radiation spectrum including CO₂ absorption bands at 1.6 μm, 2.0 μm, and 15 μm. The former two bands are used to estimate columnar concentration of CO₂; the latter is used to retrieve the vertical profile of CO₂ in the upper atmosphere above about 700 hPa pressure level. In addition, another installed on the satellite is an imaging sensor that will be used to detect clouds and aerosols: Cloud and Aerosol Imager (CAT). The Center for Climate System Research (CCSR) has contracted with the Japan Aerospace Exploration Agency (JAXA) to develop an algorithm to retrieve CO₂ concentration profiles from data measured by the thermal infrared (TIR) band of the TANSO-FTS sensor. We adopt the maximum a posteriori method (MAP) to retrieve the vertical profile of atmospheric parameters from thermal infrared spectra. Key techniques for retrieving CO₂ concentrations are 1) reduction of temperature estimation error through channel selection, 2) optimization of the initial guess for CO₂ profile based on the output from a chemical transport model (CTM), and 3) usage of data from the 1.6 μm band of TANSO-FTS as an additional constraint in retrieval of vertical profiles of CO₂. Although thermal infrared spectrum data have poor vertical resolving power for CO₂ concentration in the lower atmosphere, particularly in the boundary layer, we expect that CO₂ amount in the lower atmosphere can be deduced by substituting the upper level concentration from the columnar concentration estimated from the 1 .6 μm band data.