Showing papers in "Journal of Quantitative Spectroscopy & Radiative Transfer in 1994"

HYADES—A plasma hydrodynamics code for dense plasma studies

Abstract: The one-dimensional radiation hydrodynamics code HYADES was originally developed to simulate laboratory experiments on dense plasmas driven by intense sources of energy. The code was constructed with the objectives of providing a tool that is (1) “easy to use” by an experimentalist, (2) formulated using simple yet accurate numerical approximations to the physics models, (3) easy to modify and extend with new models, and (4) run on a variety of computers including PCs and Macs. Improvements have been made to several of the physics packages, especially the atomic physics and opacity models. Recent additions and modifications have been made to allow more realistic simulations of materials at temperatures below a few eV. These include models for materials with strength, yield, and linear heat conduction. Examples of simulations of two recent laboratory experiments demonstrates the utility of the code.

A model for temperature-dependent collisional quenching of OHA2∑+

Abstract: A model for the temperature-dependent collisional quenching of OHA2∑+ is presented. The model for quenching is based on a classical electron transfer mechanism. Predictions of the model are shown to adequately reproduce many of the experimentally observed trends: variation with collision partner, temperature, and vibrational level in OHA2∑+, and the disposition of the quenching products. A negligibly small electronic quenching cross-section is predicted for collision partners having positive ions that cannot be produced through a thermal collision with OHA2∑+. Results of the model are compared to experimentally measured cross-sections for a number of species of interest in combustion and aerothermodynamic applications. A general function for the temperature dependence of the cross-section for collisional quenching of OHA2∑+ is derived. Curve-fitting coefficients for a number of collision partners are tabulated.

Asymmetry parameters of the phase function for densely packed scattering grains

Abstract: Spatial correlation among densely packed particles can substantially change their single-scattering properties, thus making questionable the applicability of the independent scattering approximation in calculations of light scattering by planetary regoliths. The same problem arises in geophysics in light scattering computations for snow, frosts, and bare soil. In this paper, we use a dense-medium light-scattering theory based on the introduction of the static structure factor to calculate asymmetry parameters of the phase function for densely packed particles with real refractive indices 1.31 and 1.66, approximating water ice and soil particles, respectively, and imaginary refractive indices 0, 0.01, and 0.3. For sparsely distributed, independently scattering grains, the calculated asymmetry parameters are always positive and always larger than those for densely packed particles. For densely packed grains, the asymmetry parameters may be negative but only for radius-to-wavelength ratios from about 0.1 to about 0.4. With decreasing particle size, the calculated asymmetry parameters tend to zero independently of the compaction state. In the geometrical optics regime, the asymmetry parameters for densely packed scatterers are positive and very close to those for independently scattering grains. These results may have important implications for remote sensing of the Earth and solid planetary surfaces. In particular, it is demonstrated that negative asymmetry parameters derived with some approximate multiple-scattering theories may be physically irrelevant and can be the result of using an inaccurate bidirectional reflection function combined with the ill-conditionally of the inverse scattering problem.

Errors induced by the neglect of polarization in radiance calculations for rayleigh-scattering atmospheres

Abstract: Although neglecting polarization and replacing the rigorous vector radiative transfer equation by its approximate scalar counterpart has no physical background, it is a widely used simplification when the incident light is unpolarized and only the intensity of the reflected light is to be computed. We employ accurate vector and scalar multiple-scattering calculations to perform a systematic study of the errors induced by the neglect of polarization in radiance calculations for a homogeneous, plane-parallel Rayleigh-scattering atmosphere (with and without depolarization) above a Lambertian surface. Specifically, we calculate percent errors in the reflected intensity for various directions of light incidence and reflection, optical thicknesses of the atmosphere, single-scattering albedos, depolarization factors, and surface albedos. The numerical data displayed can be used to decide whether or not the scalar approximation may be employed depending on the parameters of the problem. We show that the errors decrease with increasing depolarization factor and/or increasing surface albedo. For conservative or nearly conservative scattering and small surface albedos, the errors are maximum at optical thicknesses of about 1. The calculated errors may be too large for some practical applications, and, therefore, rigorous vector calculations should be employed whenever possible. However, if approximate scalar calculations are used, we recommend to avoid geometries involving phase angles equal or close to 0 deg and 90 deg, where the errors are especially significant. We propose a theoretical explanation of the large vector/scalar differences in the case of Rayleigh scattering. According to this explanation, the differences are caused by the particular structure of the Rayleigh scattering matrix and come from lower-order (except first-order) light scattering paths involving right scattering angles and right-angle rotations of the scattering plane.

Linepak: Algorithms for modeling spectral transmittance and radiance

Abstract: A set of subroutines has been written for use in developing spectral models, with emphasis on the Earth's atmosphere. Features include rapid calculation of absorption cross section, radiance and transmission spectra for multiple gases and multiple paths. The routines are designed to allow user control of model geometry, line shape functions, band models, atmospheric layering, and spectral resolution. Numerical techniques and applications are described with examples that include a simulated limb scan retrieval and comparison to other codes.

Light scattering by polydisperse, rotationally symmetric nonspherical particles: Linear polarization

Abstract: Since most solid particles in the Earth and planetary atmospheres have irregular shapes, quantifying the effects of particle nonsphericity on the results of remote sensing of the atmosphere is an important problem. In this paper, we perform a general theoretical survey of linear polarization of light scattered by polydisperse, randomly oriented, rotationally symmetric particles of size comparable to the wavelength of radiation. Our paper deals with polydispersions of nonspherical particles because (1) averaging light-scattering characteristics over sizes provides more realistic modeling of natural particle ensembles and (2) comparisons of scattering properties of particles of a single size are usually meaningless because of the complicated interference structure and high-frequency ripple of monodisperse scattering patterns. In our computations, we use the T-matrix approach, as extended recently to randomly oriented particles by Mishchenko [ J. Opt. Soc. Amer A 8 , 871 (1991)]. Following Hansen and Travis [ Space Sic. Rev. 16 , 527 (1974)], we assume that the scattering properties of polydisperse particles depend primarily on only the effective size parameter and effective variance of the size distribution, the particular shape of the distribution being of minor importance. Therefore, to describe the dispersion of particle sizes in the ensemble, we employ a convenient power law distribution of particle equivalent-sphere size parameters. Size- averaged light-scattering characteristics are calculated by numerically integrating monodisperse quantities using a Gaussian quadrature formula. The results of extensive numerical calculations for particles of different shape and refractive index are presented in the form of color contour diagrams of linear polarization as a function of scattering angle and effective equivalent-sphere size parameter. The influence of particle size distribution, shape, and refractive index on the polarization patterns is examined in detail and implications for polarimetric remote sensing of nonspherical aerosols are discussed. The diagrams displayed include calculations for over 150,000 different monodisperse particles in rndom orientation with equivalent-sphere size parameters up to 30 and may be used to interpret results of laboratory measurements and remote observations of light scattering by small particles.

BANDPAK: Algorithms for modeling broadband transmission and radiance

Abstract: A library of subroutines has been written for rapid modeling of broadband atmospheric emission and transmission. Features include multiple gases, multiple bandpasses, multiple atmospheric paths, accurate line overlap correction, ability to model any observation geometry, and complete control of atmospheric layering and state definitions. Numerical procedures and examples of use are described.

Collisional broadening of water vapor lines—I. A survey of experimental results

Abstract: The present work is a critical survey of experimental results on the pressure broadening of H 2 16 O absorption lines. A systematic collection of the published water vapor collisional broadening measurements by various perturbers has been made. This database includes about 4000 H 2 O line-width measurements, 500 for which the temperature dependence has been studied. Although many experiments are available, much remains to be done in regards of the data required for practical applications. The collected half-widths sets have been used for intercomparison between different works and for study of the influence of the vibrational states, collision partner, and temperature on broadening. The results show that measurements by different authors are often inconsistent, probably on account of an underestimation of experimental errors. Furthermore, since the influence of vibration remains generally within measurement uncertainties, no clear conclusion concerning vibrational dependence of half-widths can be drawn. Finally, filtering of the data sets has enabled determination of reliable values for some widely studied lines. The latter should be useful for test of experimental procedures, remote sensing, and validation of theoretical models. Recommendations for future measurements in order to complete these data sets are also made.

Collision broadening and shift of NO γ(0, 0) absorption lines by O2 and H2O at high temperatures

Abstract: Collision-broadened absorption lineshapes of the A ← X (0, 0) transitions of NO near 225 nm were measured behind reflected shock waves in a shock tube by using the frequency-doubled output of a narrow-linewidth, rapid-tuning cw ring dye laser. The profiles of the transitions, perturbed by a single bath species, either H 2 O or O 2 , were fit assuming Voigt lineshapes to derive collision-induced width coefficients (2γ). The collision-induced shift coefficient (δ) was also measured, with reference to the same NO feature recorded simultaneously in absorption across a low-pressure cell of pure NO. For both perturbers, an inverse power-law for the temperature dependence was obtained for both 2γ and δ. Over the temperature range 1000–2000 K, 2γ for the case of O 2 as perturber was roughly 80% of that measured for the case of H 2 O as perturber, and δ for both perturbers were the same within approximately 10%. Dependence of 2γ and δ on the ground-state energy of the A ← X (0, 0) transitions of NO were discernible for the case of H 2 O as perturber. All perturbers induced slight asymmetries and narrowing of the lineshape.

Correlation transfer: development and application.

Abstract: A correlation transfer equation for multiple scattering of light through suspensions of diffusing particles is derived from multiple scattering theory. Because of the formal similarity between the correlation equation and the radiative transfer equation, radiative transport solution techniques are applied to obtain solutions for the field correlation function in isotropic one-dimensional media. A three-term Legendre expansion for the angularly dependent single scattering function (g') in the correlation integral equation is used to obtain approximate numerical solutions for the correlation function. Graphical results are presented for the correlation in both the forward and backward directions for a finite medium and for backscattering in the case of an infinite medium. Experimental results are also presented and they show improved agreement with the three-term Legendre expansion of g' as compared to the one or two-term expansions. Correlation transfer results are shown to agree well with both the diffusion limit and the single scattering limit predictions. The motion of particles in fluid/particle suspensions gives rise to temporal fluctuations in the intensity of multiply scattered light. From the measured temporal autocorrelation functions, one can in principle, determine fluid/particle properties such as particle diameter, fluid viscosity, and diffusion constants. These measurements can be used to characterize a variety of suspensions such as gels and paint. However, for accurate characterization, the suspensions must be very dilute so that the Born approximation may be employed.' For optically dense suspensions, the diffusion approximation has successfully been used to study the time dependence of the intensity fluctuations in what has been termed diffusive wave spectroscopy (DWS).2.3 Another related theoretical approach that has been developed to calculate the temporal autocorrelation function of multiply scattered light was employed by Stephen4 using a diagram- matic description of the scattering from the random fluctuations in the dielectric constant. The propagation of light is still assumed to be diffusive in Stephen's derivations. Arbitrary orders of scattering could not be predicted and modeled by either of the two diffusion methods above. For semi-infinite media, experimental results show that the backscattered correlation function exhibits an exponential decay in the square root of delay time over the full range of the delay times measured.2.3.5 The theoretical diffusive wave results (DWS) for backscattering do produce precisely this decay rate for boundary conditions assuming a single deposition depth for the incident light. If the deposition depth is exponentially distributed and decaying with increasing distance from the surface of the medium (Beer's law), the predicted correlation function shows even greater departures from the experimentally observed exponentiality.6 This problem has been attributed to the continuous light path length distribution assumption made in DWS. This assumption includes paths which tend to zero length and correspond to very slowly decaying correlation functions at large delay times. These decay rates are much slower than the expected decay rate for backscat- tering and so contribute to a theoretical anomaly. This is partially remedied by the assertion that the deposition depth distribution is narrowly distributed near the average scattering length' (not following Beer's law). However, this result is essentially the original DWS result described above with the deposition depth identified as the average scattering length.

Approximate intensities of CO2 hot bands at 2.7, 4.3, and 12μm for high temperature and medium resolution applications

Abstract: An approximate CO2 spectroscopic data base suitable for high temperature and medium resolution applications has been created. Intensities of 12C16O2 and 13C16O2 hot bands centered in the 2.7, 4.3, and 12μm spectral regions have been calculated from cold band intensities reported in the 1992 edition of the HITRAN data base by using pragmatic expressions. The energies of the corresponding levels missing in HITRAN have been computed by diagonalization of the Fermi matrix associated to different polyads. The new parameters have been added to the level and band tabulation used in HITRAN '92, which concern the eight most abundant CO2 isotopes. The entire list has then been used to generate line parameters reported in the new data base. Line-by-line calculations using data from HITRAN and this base are compared with available experimental spectra at high temperature (750–2850 K) and medium resolution (1–3 cm-1). A good agreement is obtained when using the new base.

A compilation of first-order line-mixing coefficients for CO2 Q-branches

Abstract: A parameterization of first-order line-mixing in CO2 Q-branches is presented for use in atmospheric radiative transfer codes. Regression coefficients for the temperature dependence of the first-order line-mixing parameters for each J in 11 of the strongest Q-branches between 600 and 3000/cm are given. These coefficients may only be used with the line strengths and widths reported in the HITRAN92 line compilation; otherwise large errors will be introduced into the calculated line shape. Other potential problems in the implementation of first-order line-mixing in radiative transfer codes are also discussed.

T.D.S. spectroscopic databank for spherical tops: DOS version

Abstract: T.D.S. is a computer package concerned with high resolution spectroscopy of spherical top molecules like CH 4 , CF 4 , SiH 4 , SiF 4 , SnH 4 , GeH 4 , SF 6 , etc. T.D.S. contains information, fundamental spectroscopic data (energies, transition moments, spectroscopic constants) recovered from comprehensive modeling and simultaneous fitting of experimental spectra, and associated software written in C. The T.D.S. goal is to provide an access to all available information on vibration-rotation molecular states and transitions including various spectroscopic processes (Stark, Raman, etc.) under extended conditions based on extrapolations of laboratory measurements using validated theoretical models. Applications for T.D.S. may include: education/training in molecular physics, quantum chemistry, laser physics; spectroscopic applications (analysis, laser spectroscopy, atmospheric optics, optical standards, spectroscopic atlases); applications to environment studies and atmospheric physics (remote sensing); data supply for specific databases; and to photochemistry (laser excitation, multiphoton processes). The reported DOS-version is designed for IBM and compatible personal computers.

Configuration interaction in LTE spectra of heavy elements

Abstract: We present a method for including the effects of configuration interaction (CI) between relativistic subconfigurations of an electron configuration in the calculation of emission and absorption spectra of plasmas in local thermodynamic equilibrium (LTE). Analytical expressions for the correction to the intensities, owing to CI, of an unresolved transition array (UTA) and of a supertransition array (STA) are obtained when the correction is small compared to the spin-orbit splitting, bypassing the need to diagonalize energy matrices. These expressions serve as working formulas in the STA model and, in addition, reveal a priori the conditions under which CI effects are significant. Examples of the effect are presented.

Mid-infrared extinction by sulfate aerosols from the Mt Pinatubo eruption

Abstract: Quantitative measurements of the wavelength dependence of aerosol extinction in the 750-3400/cm spectral region have been derived from 0.01/cm resolution stratospheric solar occultation spectra recorded by the ATMOS (Atmospheric Trace Molecule Spectroscopy) Fourier transform spectrometer about 9 1/2 months after the Mt Pinatubo volcanic eruption. Strong, broad aerosol features have been identified near 900, 1060, 1190, 1720, and 2900/cm below a tangent height of approximately 30 km. Aerosol extinction measurements derived from approximately 0.05/cm wide microwindows nearly free of telluric line absorption in the ATMOS spectra are compared with transmission calculations derived from aerosol size distribution profiles retrieved from correlative SAGE (Stratospheric Aerosol and Gas Experiment) II visible and near i.r. extinction measurements, seasonal and zonally averaged H2SO4 aerosol weight percentage profiles, and published sulfuric acid optical constants derived from room temperature laboratory measurements. The calculated shapes and positions of the aerosol features are generally consistent with the observations, thereby confirming that the aerosols are predominantly concentrated H2SO4-H2O droplets, but there are significant differences between the measured and calculated wavelength dependences of the aerosol extinction. We attribute these differences as primarily the result of errors in the calculated low temperature H2SO4-H2O optical constants. Errors in both the published room temperature optical constants and the limitations of the Lorentz-Lorenz relation are likely to be important.

Spectral absorption-coefficient data on HCFC-22 and SF6 for remote-sensing applications

Abstract: Spectral absorption-coefficients (cross-sections) kappa(sub nu) (/cm/atm) have been measured in the 7.62, 8.97, and 12.3 micrometer bands of HCFC-22 (CHClF2) and the 10.6 micrometer bands of SF6 employing a high-resolution Fourier-transform spectrometer. Temperature and total pressure have been varied to simulate conditions corresponding to tropospheric and stratospheric layers in the atmosphere. The kappa(sub nu) are compared with values measured by us previously using a tunable diode laser spectrometer and with the appropriate entries in HITRAN and GEISA, two of the databases known to the atmospheric scientist. The measured absolute intensities of the bands are compared with previously published values.

A radiative-transfer inverse-source problem for a sphere.

Abstract: A sphere-to-plane transformation technique and the spherical-harmonics method are used to develop a solution to an inverse-source problem for radiative transfer in a spherical body. It is assumed that, with the exception of the inhomogeneous source term, all aspects of the radiation-transport problem are known, and we seek to determine the source term from a specified angular distribution of radiation that exits the surface of the sphere.

Atomic transition probabilities in RuI

Abstract: Accurate absolute atomic transition probabilities are reported for 482 lines of RuI. These are determined by combining branching fractions, measured using the 1.0 m Fourier transform spectrometer at the National Solar Observatory, with radiative lifetimes, measured using time-resolved laser induced fluorescence.

Spectroscopic temperature measurements in a decaying laser-induced plasma using the C2 Swan system

Abstract: Spontaneous emission spectra of C2 Swan bands were recorded well after i.r. 1064 nm Nd: YAG laser-induced optical breakdown of carbon monoxide. Temperatures in excess of 6000 K were determined using fits to synthetic diatomic molecular spectra.

Thermal infrared absorption coefficients of CFC-12 at atmospheric conditions

Abstract: Spectral absorption coefficients k v (cm -1 atm -1 ) have been measured in the 9 and 11 μm bands of CFC-12 (CF 2 Cl 2 ) using a high-resolution Fourier transform spectrometer. Temperature and total (broadening) pressure have been varied to obtain results at conditions representative of tropospheric and stratospheric layers of the atmosphere. The measured absolute intensities (in units of 10 -17 cm.molecule -1 ) of the 9 and 11 μm bands are 7.595 ±0.070 and 5.750 ±0.068, respectively.

Transport in renewal statistical media: Benchmarking and comparison with models

Abstract: We give detailed numerical benchmark results in planar geometry for particle transport and radiative transfer including scattering in renewal statistical media. The results given are the probabilities of reflection and transmission and three different types of ensemble-averaged flux for all interior location points. Our results confirm previous evidence that different statistics yield different results and that mean and variance are the parameters of the statistical distributions that have the most influence on the transport problem. In a second part we solve numerically three models and compare them with our benchmark results. The first two models are integro-differential models that were developed for Markovian statistics, but can be partially corrected for non-Markovian statistics. The third model is an integral model developed for stochastic transport without scattering which we extended to include scattering. The comparisons we make underline the importance of having extensive and complete benchmark calculations against which to test proposed models.

A coolable long path absorption cell for laboratory spectroscopic studies of gases

Abstract: A long path absorption cell (Long White Cell) which has been designed and built for laboratory spectroscopic studies of gases found in terrestrial and planetary atmospheres is described. Factors influencing the design and construction are discussed, including aspects of the optical, mechanical, cryogenic, vacuum, gas handling and safety systems, and the pressure and temperature monitoring systems. The practical capabilities of the cell include absorber pathlengths up to 512 m, gas sample pressures up to 5 bar and temperatures between 190 and 300 K, and the suitability for use with corrosive and flammable gases. The performance of the cell is discussed in relation to spectroscopic measurements of mixtures of gaseous methane and hydrogen.

Determination of broadening coefficients and intensities for overlapping spectral lines with application to the QR (3,K) lines in the v3 band of CH353Cl

Abstract: We have developed a method of extracting individual line parameters from overlapping absorption spectra recorded with a tunable diode-laser spectrometer. Assuming Voigt profiles for the individual lines, the overall absorption is expressed as the sum of the absorption coefficients of the recorded lines plus a small contribution due to neighboring lines. The computational procedure has been applied to the four Q R (3, K ) lines, self-broadened and broadened by N 2 ,O 2 , Ar and He, in the v 3 band of CH 35 3 Cl at 736.3 cm -1 . The intensities and collision-broadened widths are found to be linear functions of the broadener pressures, which implies negligible line-mixing effects between the K components. For all the perturbers considered the broadening coefficients of the Q R (3, K lines decrease significantly as K increases, in agreement with theoretical results.

Estimation of the temperature profile in a cylindrical medium by inverse analysis

Abstract: An inverse radiation problem for determining the unknown temperature distribution in a one-dimensional absorbing, emitting, scattering cylindrical medium from the knowledge of the exit radiation intensities is presented. The inverse radiation problem is constructed as an optimization problem in finite-dimensional space and the conjugate gradient method is used for its solution.

The Smithsonian Astrophysical Observatory database SAO92.

Abstract: The Smithsonian Astrophysical Observatory (SAO) maintains a molecular line database (the SAO line database) for analysis of atmospheric spectra in the far i.r. and longer-wave mid i.r., from 10-800 cm -1 . This database combines the best currently available line parameters, including the HITRAN 1.2 molecular database, the JPL submillimeter, millimeter, and microwave spectral line catalog 3 (JPLSMM), and other available measurements and calculations. The current version of the database contains 154.895 lines from H 2 O, CO 2 , O 3 , N 2 O, CO, CH 4 , O 2 (including the 1 Δ state), NO, SO 2 , NO 2 , NH 3 , HNO 3 , OH, HF, HCl, HBr, HI, ClO, OCS, H 2 CO, HOCl, HCN, H 2 O 2 , O( 3 P ), and HO 2 . The database is available in both HITRAN-type 80 character (SAO92) and 100 character (SAO92A) formats. 1. L.S. Rothman, R.R. Gamache, A. Goldman, L.R. Brown, R.A. Toth, H.M. Pickett, R.L. Poynter, J.-M. Flaud, C. Camy-Peyret, A. Barbe, N. Husson, C.P. Rinsland, and M.A.H. Smith, Appl. Opt. 26 , 4058 (1987). 2. L.S. Rothman, R.R. Gamache, R.H. Tipping, C.P. Rinsland, M.A.H. Smith, D. Chris Benner, V. Malathy Devi, J.-M. Flaud, C. Camy-Peyret, A. Perrin, A. Goldman, S.T. Massie, L.R. Brown, and R.A. Toth, JQSRT . 48 , 469 (1992). 3. R.L. Poynter and H.M. Pickett, Submillimeter millimeter and microwave spectral line catalog, Publ. 80-23, revision 2, Jet Propulsion Laboratory, Pasadena, CA (1984).

Ground-based visible measurements at the Jungfraujoch station since 1990

Abstract: Ground-based observations of nitrogen dioxide and ozone total columns have been performed since June 1990 at the International Scientific Station at the Jungfraujoch (45°N, 8°E). Measurements are made twice a day, at sunrise and sunset, by looking at the sunlight scattered at zenith in the visible range. NO2 and O3 vertical abundances are deduced by the differential absorption method. The error sources of the method are discussed in detail. For most observation conditions, the precision of measurement is estimated at about 11% for NO2 and 6% for O3. However larger errors might be encountered occasionally due to tropospheric pollution or enchanced multiple scattering in thick clouds. It is shown that the signature of such events can be detected in the evolution of the retrieved vertical column during the twilight period. A systematic method to detect and reject data significantly biased is described and applied to the NO2 time-series of measurements.

Measurement of the absorption cross-sections of CFC-11 at conditions representing various model atmospheres

Abstract: Absorption cross-sections, K(sub V)(/(cm)(atm)), have been measured in the 9.2 and 11.8 micrometer bands of CFC-11 (CCl3F) using a high-resolution Fourier transform spectrometer. Temperature and total (N2-broadening) pressure have been varied to obtain results at conditions representative of the atmosphere. The measured absolute intensities (in units of 10(exp -17) cm/molecule of the 9.2 and 11.8 micrometer bands are 2.591 +/- 0.013 and 6.974 +/- 0.038, respectively.

The GEISA data bank in 1993: A PC/AT compatible computers' new version

Abstract: An IBM PC AT/XT compatible version of the GEISA database has been recently created with the purpose of extending its use to potential non mainframe users and because of the now generalized employment of personal computing facilities. Thanks to a collaboration between the Laboratoire de Meteorologie Dynamique du CNRS, in France, and the Laboratory of Theoretical Spectroscopy of Institute of Atmospheric Optics, in Russia, an enhanced and extended management system of GEISA has been built up. This paper provides an overview of the new GEISA-PC system, and details the updates of the database contents since its previous edition.

Radiative dissipation in planar gas-soot mixtures

Abstract: A theoretical expression for the gas cooling rate (radiative dissipation) in planar mixtures of soot and combustion product gases is derived that is valid for all degrees of optical thickness. The absorption terms are reduced to numerical quadrature over the coordinate normal to the flame structure, and describe soot and gas self-absorption, as well as soot-gas spectral overlap effects. Numerical examples illustrating the effect of radiative cooling on NO production in a model, sooting, opposed jet diffusion flame are given.

A convergent theory of Stark broadening of hydrogen lines in dense plasmas

Abstract: A generalized semi-classical theory of Stark broadening is developed that is free from a shortcoming of the standard semi-classical theories of Stark broadening which were intrinsically divergent at small impact parameters. A convergency of the present theory is achieved by taking into account on equal footing both a “dynamic” splitting of Stark sublevels caused by one of the components of the electron microfield and a quasistatic splitting of Stark sublevels caused by ion microfield (only the latter was allowed for in the standard theories). The presented generalized theory is developed analytically to the same level as the standard theories: it substitutes the “broadening” function C ST ( Z ) of the standard theories by a generalized but still elementary function C ( Z ). The generalized theory embraces the standard theories as one of its limiting cases corresponding to relatively low densities of a plasma. However for dense plasmas the predictions differ: our results demonstrate that the standard theories overestimate an electron impact broadening for high density plasmas.