Showing papers in "Journal of Quantitative Spectroscopy & Radiative Transfer in 1993"
TL;DR: In this paper, an absorption-line blackbody distribution function for H2O is presented, which provides an efficient means for total radiative transfer calculations by eliminating the need to specify a path-length required by current narrow and wide band models.
Abstract: An absorption-line blackbody distribution function for H2O which provides an efficient means for total radiative transfer calculations is presented. The function eliminates the need to specify a path-length required by current narrow and wide band models since the basic radiative property is the locally defined absorption coefficient. This allows the model to be used with arbitrary solution methods of the radiative transfer equation which requires the absorption coefficient as input. A simple mathematical correlation is presented for use in computer algorithms. A few sample calculations of total emissivity as well as numerical solutions to the radiative transfer equation with the use of the distribution function are performed. The model shows good agreement with Hottel's total emissivity data. There is also very good agreement between the model and computationally intensive line-by-line calculations in isothermal media of uniform composition. The function may also be used for approximate calculations in non-uniform media.
145 citations
TL;DR: In this paper, a data file of the cross-sections of SO2 was assembled from 106.1 to 403.7 nm at a resolution of 0.1 nm, where photoplate data were compared with spectrophotometric data.
Abstract: Available spectrophotometric data on absorption cross-sections of SO2 for the gas phase from 106 to 403 nm at 293 ± 10 K have been evaluated and, where necessary, converted to a digital form. Plotting and comparing various overlapping data sets has demonstrated that systematic errors in wavelength and cross-section exist in the data sets. A scheme, which uses newer data sets that were recorded over limited wavelength ranges, to correct the wavelengths and cross-sections of older data sets, is discussed. In one region photoplate data were compared with spectrophotometric data. The spectral regions where reinvestigation is warranted are discussed. A data file of the cross-sections of SO2 was assembled from 106.1 to 403.7 nm at a resolution of 0.1 nm.
143 citations
TL;DR: In this paper, branching ratios for 329 emission lines from 56 levels in Ar I and Ar II were reported and used to calibrate the relative detection efficiency of a spectrometer over the wavelength range 2100-45914 A.
Abstract: Branching ratios are reported for 329 emission lines from 56 levels in Ar I and Ar II. These branching ratios may be used to calibrate the relative detection efficiency of a spectrometer over the wavelength range 2100–45914 A.
98 citations
TL;DR: In this paper, a series of molecular band models were fitted to these spectra at 10 cm -1 resolution, showing that the Goody and Malkmus random band models with the Voigt lineshape provided the best fits to the data.
Abstract: Long-pathlength self- and H 2 -broadened absorption spectra of CH 4 have been recorded from 2000 to 9500 cm -1 at a resolution of 0.25 cm -1 . Thesespectra were obtained for a wide range of conditions relevant to the atmosphere of Jupiter, including nominal temperatures of 190, 240, and 296 K, pathlenghts from 64 to 512 m, and pressures from 0.2 to 700 torr, giving CH 4 column abundances from 0.016 to 530 m-amagat. A series of molecular band models were fitted to these spectra at 10 cm -1 resolution, showingthat the Goody and Malkmus random band models with the Voigt lineshape provided the best fits to the data. The Goody-Voigt model was subsequently used to calculate the level in the Jovian atmosphere that will be sounded by observations of CH 4 absorption, and estimates were made of the accuracy to be expected if this model were used to retrieve atmospheric parameters.
93 citations
TL;DR: A new and general method is presented for the solution of complex multi-level non-LTE radiative transfer problems both in static and moving media and is able to treat both active continua and overlapping lines with relatively small amount of computer resources.
Abstract: We present a new and general method for the solution of complex multi-level non-LTE radiative transfer problems both in static and moving media. The method is based on the approximate Λ-iteration method and is a direct extension of the scheme devised by Rybicki and Hummer (1991). We demonstrate that this method is able to treat both active continua and overlapping lines with relatively small amount of computer resources. Some simplified test cases are presented and discussed.
90 citations
TL;DR: In this article, the authors used the Nimbus 4 Infrared Interferometer Spectrometer (IRIS) to examine the i.r. optical characteristics of these clouds and found that the seasonal cloud cover produced by these thin cirrus exceeds 50% near the central regions of the equatorial western Pacific surrounding Indonesia.
Abstract: Over the convectively active tropical ocean regions, measurements made from space in the infrared (i.r.) and visible have revealed the presence of optically thin cirrus clouds which are quite transparent in the visible and nearly opaque in the infrared. The Nimbus 4 Infrared Interferometer Spectrometer (IRIS), which has a field of view (FOV) of almost-equal-to 100 km, has been utilized to examine the i.r. optical characteristics of these cirrus clouds. From the IRIS data it has been observed that these optically thin cirrus clouds prevail extensively over the ''warm pool'' region of the equatorial western Pacific surrounding Indonesia. It is found that the seasonal cloud cover produced by these thin cirrus exceeds 50% near the central regions of the ''warm pool''. For most of these clouds, optical thickness in the infrared is < 2. It is deduced that dense cold anvil clouds associated with deep convection spread extensively and are responsible for the formation of the thin cirrus. This is supported by the observation that the coverage of the dense anvil clouds is an order of magnitude less than that of the thin cirrus. Observations made by the Earth Radiation Budget Experiment (ERBE) reveal that the ''warm pool'' region constitutes a local maximum in net input of radiative energy. From these observations, together with a simple radiative energy balance model, we have inferred that the greenhouse effect produced by the optically thin cirrus clouds can be a significant factor in maintaining the ''warm pool''.
87 citations
TL;DR: In this paper, the spherical-harmonics method is used to develop a solution to an inverse source problem in radiative transfer, assuming that, with the exception of the inhomogeneous source term, all aspects of the radiation-transport problem are known.
Abstract: The spherical-harmonics method is used to develop a solution to an inverse source problem in radiative transfer. 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 inhomogeneous source term from specified angular distributions of radiation exiting the two surfaces of a homogeneous plane-parallel medium. Anisotropic scattering is included in the monochromatic radiative-transfer model and general reflecting boundary conditions are considered.
70 citations
TL;DR: In this article, the problem of radiation transfer in three-dimensional atmosphere-vegetation media is formulated and the boundary condition is defined in terms of vegetation canopy bidirectional reflectance factors to be evaluated from a numerical solution of the 3D canopy radiative transfer equation.
Abstract: The problem of radiation transfer in three-dimensional atmosphere-vegetation media is formulated in this paper. The atmosphere is treated as a horizontally homogeneous medium but with spatially varying anisotropic lower boundary. The boundary condition is defined in terms of vegetation canopy bidirectional reflectance factors to be evaluated from a numerical solution of the three-dimensional canopy radiative transfer equation. Numerical results obtained with the discrete ordinates method are in good agreement with the Monte Carlo results of Pearce and field soybean reflectance data of Ranson et al.
66 citations
TL;DR: In this article, a ring dye laser system using intracavity BBO frequency doubling was used to measure the absorption of narrow-line laser radiation by methyl radicals produced at high temperatures near 216nm.
Abstract: Absorption of narrow-line laser radiation by methyl radicals produced at high temperatures was studied in the Herzberg β 1 band near 216nm. cw radiation for these measurements was generated in a ring dye laser system using intracavity BBO frequency doubling. Methyl radicals were produced by the shock wave heating of five selected source compounds: azomethane, methyl iodide, tetramethyl tin, tetramethyl silane and ethane. The variation with wavelength of the CH 3 absorption coefficient between 210 and 225 nm was measured at 1625 K and 1.25 atm using ethane/Ar and methyl iodide/Ar gas mixtures. The variation of the absorption coefficient with temperature from 1350 to 2450 K was measured at 216.615 nm using four source compounds. Using this wavelength for CH 3 measurements resulted in a typical detectivity limit of 2ppm at 1650 K, 1 atm, L = 10 cm, with a SNR of unity and a detection bandwidth of 500 kHz.
60 citations
TL;DR: In this paper, the authors used a difference-frequency laser spectrometer to measure N 2, O 2, H 2, Ar- and He-broadening coefficients and pressure shifts for Q - and R -branch transitions in the ν 1 fundamental band of ammonia.
Abstract: N 2 -, O 2 -, H 2 -, Ar- and He-broadening coefficients and pressure shifts have been measured for Q - and R -branch transitions in the ν 1 fundamental band of ammonia using a difference-frequency laser spectrometer. The J - K dependence of the broadening coefficients is much smaller than previously observed for self broadening of NH 3 . Semiclassical line broadening calculations for N 2 broadening are in reasonable quantitative agreement with the data, but they also exaggerate the J - K dependence. Dicke narrowing is observed as strong deviations from Voigt profiles at intermediate pressures and provides estimates for optical diffusion constants which correlate well with the mass diffusion constants for NH 3 in the various buffer gases.
56 citations
TL;DR: In this article, the divergence of the net radiative flux is formulated in terms of wide-band absorptance model parameters for combustion products, and is valid for all degrees of optical thickness.
Abstract: An expression is derived for the radiative source term governing the interaction of molecular gas band radiation and flow in nonhomogeneous, plane-parallel reacting flow problems. The divergence of the net radiative flux is formulated in terms of wide-band absorptance model parameters for combustion products, and is valid for all degrees of optical thickness. When optical thickness is finite, the net absorption is obtained by integrating the radiation field solution over the band lineshapes and taking hemispherical averages. Illustrative calculations for counterflow diffusion flames will be discussed.
TL;DR: In this paper, experimental and theoretical studies of medium infrared absorption by pure water vapor were performed in the 1900-2600 cm and 3900-4600 cm regions for temperatures and pressures of 500-900 K and 0-70 atm, respectively.
Abstract: Results of experimental and theoretical studies of medium infrared absorption by pure water vapor are reported. The experiments were performed in the 1900-2600/cm and 3900-4600/cm regions for temperatures and pressures of 500-900 K and 0-70 atm, respectively. The results are consistent with data in the literature and enable the determination of continuous absorption parameters.
TL;DR: In this paper, the authors measured self-, N2-and ar-broadening coefficients for the stretch-bend infrared combination bands nu-1+nu-1/2 (4004/cm) of HCN and C2H2, using a tunable difference-frequency laser and found that 35-70 percent of the broadening may be due to other collisional mechanisms such as cross-relaxation to the degenerate H state vibrational level.
Abstract: Self-, N2- and Ar-broadening coefficients were measured for the stretch-bend infrared combination bands nu-1 + nu-1/2 (4004/cm) of HCN and nu-1 + nu-1/5 (4091/cm) of C2H2, using a tunable difference-frequency laser. At atmospheric pressures, the Q branches of these bands exhibit significant rotational narrowing or line mixing. The broadening coefficients are fit with empirical rotationally inelastic collision rate laws, which are then used to model the line mixing in the overlapped Q-branch profiles. Simple energy gap fitting laws appear to be suitable for the shorter-range intermolecular quadrupole-quadrupole and induction forces, whereas an energy-corrected-sudden scaling law works better for the longer-range dipole-dipole and dipole-quadrupole collision partners. In all cases, the line-coupling coefficients are substantially reduced from the rotationally inelastic rates fit to the broadening coefficients, indicating that 35-70 percent of the broadening may be due to other collisional mechanisms such as cross-relaxation to the degenerate H state vibrational level.
TL;DR: The algorithm consists of series, rational approximations and Gauss-Hermite integrations which makes it suitable as a general purpose software module for a wide variety of uses, including a Voigt function standard.
Abstract: A complex Voigt lineshape algorithm is presented whose maximum relative error over the complex plane is less than 1 x 10(exp -8). The algorithm consists of series, rational approximations and Gauss-Hermite integrations which makes it suitable as a general purpose software module for a wide variety of uses, including a Voigt function standard.
TL;DR: In this article, data processing and calibration methods are described for tunable diode laser absorption spectrometers which produce harmonic absorption spectra as raw data for measuring gas mixing ratios down to parts-per-trillion levels at a variety of pressures.
Abstract: Data processing and calibration methods are described for tunable diode laser absorption spectrometers which produce harmonic absorption spectra as raw data for measuring gas mixing ratios down to parts-per-trillion levels at a variety of pressures. The methods, which take advantage of modern computer speed, memory, and data storage capabilities, are applicable to the detection of weakly absorbing gases in quantitative industrial monitoring, in addition to aircraft and balloon atmospheric measurements for which they were designed. Algorithms for calibration and data analysis, including rejection of erroneous spectra, variation of effective integration time, spectral alignment prior to averaging, and plotting and archiving of results, have been tested on actual stratospheric laser spectra recorded by the Aircraft Laser Infrared Absorption Spectrometer (ALIAS) spectrometer in numerous flights of NASA's ER-2 aircraft.
TL;DR: In this article, a procedure for obtaining atom-atom intermolecular potentials from the two-center expansion using symbolic manipulations in FORTRAN and MATHEMATICA on a computer is described.
Abstract: A procedure for obtaining atom-atom intermolecular potentials from the two-center expansion using symbolic manipulations in FORTRAN and MATHEMATICA on a computer is described. The atom-atom potential for an XY 2 molecule ( C 2 v symmetry) and a linear, AB, molecule with the XY 2 molecule positioned in the molecule-fixed axes in two different orientations (representations), labeled II R and II L , are calculated. It has been found that the previous development of the atom-atom potential in the II R representation is incorrect and leads to a mixed formulation with electrostatic terms in the I R and atom-atom terms in the III L representation. Broadening-coefficient calculations presented here show that when the correct potential is used anomalous oscillations in the Ka ″ = 1 transitions for O 3 broadened by N 2 disappear. Further investigation has shown that the variations can be associated with particular quantum state symmetries. Improved agreement with the experimental measurements is observed.
TL;DR: In this paper, the authors measured self-broadening coefficients, pressure shifts, and integrated intensities for Q- and R-branch transitions in the nu-1 fundamental band of ammonia using a difference-frequency laser spectrometer.
Abstract: Self-broadening coefficients, pressure shifts, and integrated intensities have been measured for Q- and R-branch transitions in the nu-1 fundamental band of ammonia using a difference-frequency laser spectrometer. A strong, systematic J and K dependence of the broadening coefficients, reminiscent of the ground-state inversion transitions, is observed and compared with semiclassical line broadening calculations. Dicke narrowing is evident at intermediate pressures for the sharpest lines, primarily the R(J, 0) transitions. Incipient line mixing is apparent in the Q branch at pressures above about 0.1 bar.
TL;DR: In this article, an analysis of 29 room-temperature laboratory absorption spectra of a dilute CH4 sample in dry air, N2, and O2 at total pressures ranging from 60 to 550 torr, yielding values of pressure-broadening and pressure-induced-shift coefficients for more than 450 vibration-rotation transitions in the nu(3), nu(2) + nu(4), and 2nu(2)-super-2 bands of (C-12)H4.
Abstract: Results are presented of an analysis of 29 room-temperature laboratory absorption spectra of a dilute CH4 sample in dry air, N2, and O2 at total pressures ranging from 60 to 550 torr, yielding values of pressure-broadening and pressure-induced-shift coefficients for more than 450 vibration-rotation transitions in the nu(3), nu(2) + nu(4), and 2nu(2)-super-2 bands of (C-12)H4. Comparisons of the present results for the nu(3) and nu(2) + nu(4) bands with previous measurements on other bands and isotopes of CH4 show that, for a given transition, broadening by air and N2 are nearly equal, and broadening by O2 is smaller by less than 10 percent. It is also found that the pressure shift coefficients are more vibrational dependent than the pressure broadening coefficients.
TL;DR: In this article, a one-dimensional radiation-hydrodynamics code called SARA (Synthetically Accelerated Radiation-Hydroynamics Algorithm) which solves the multigroup radiation transport equations implicitly is presented.
Abstract: Recently, we have developed a one-dimensional radiation-hydrodynamics code called SARA (Synthetically Accelerated Radiation-Hydrodynamics Algorithm) which solves the multigroup radiation transport equations implicitly. A high order differencing scheme as well as multifrequency grey synthetic acceleration techniques are used to obtain a robust algorithm that can be used for a large variety of energy transport problems. The advantages of such an algorithm are, first, that it solves the true (Sn) transport equations, secondly, a positive differencing scheme which verifies the asymptotic diffusion limit is used, and, finally, the Sn equations are accelerated by the S2 synthetic acceleration method, which allows the acceleration of high order schemes in plane and curvilinear geometries. The code has been validated with some Marshak wave propagation problems found in the bibliography, and successfully used to simulate the conversion experiments of laser and ion beams into X-rays.
TL;DR: An integral method of solving the Holstein-Biberman equation based on a propagator function is described in this paper, which is used to solve the equation with a Lorentz lineshape in an infinite plane parallel geometry and a hollow spherical geometry.
Abstract: An integral method of solving the Holstein-Biberman equation based on a propagator function is described This method is used to solve the equation with a Lorentz lineshape in an infinite plane parallel geometry and a hollow spherical geometry The method is ideal for solving for both the time dependent and the steady state density of resonance atoms which results from an arbitrary production rate per unit volume The propagator function method is 100 times faster than the Monte Carlo method The greater speed of the propagator function method makes it well suited to fully self-consistent kinetic simulations of glow discharge plasmas
TL;DR: In this article, the authors used the KPNO McMath FTS with spectral resolution of 0.005 cm -1 and a signal-to-noise ratio of 100 or more.
Abstract: Hydrogen-broadening of a large number of methane lines in the v 4 band has been measured at room temperature and 200 K (determined from the rotational temperature). The measurements were obtained using the KPNO McMath FTS with spectral resolution of 0.005 cm -1 and a signal-to-noise ratio of 100 or more. Hydrogen pressures between 250 and 600 torr and methane pressures up to 2 torr were utilised. The spectra were analyzed using a parametrised least-squares fitting procedure.
TL;DR: In this paper, the collisional broadening and line shift of the A2Sigma(+)-X2Pi system of a flat flame H2-air burner were measured using a singlemode, narrow linewidth, frequency-doubled ring dye laser operating near 283 nm.
Abstract: Measurements of the collisional broadening and line shift of the (1,0) band of the A2Sigma(+)-X2Pi system of OH are reported in atmospheric pressure hydrogen-air combustion gases. The measurements were made using a single-mode, narrow linewidth, frequency-doubled ring dye laser operating near 283 nm. The OH was generated in the combustion gases of a flat flame H2-air burner. Collisional broadening parameters for equilibrium mixtures of H2, O2, H2O, and N2 were obtained spanning a range of fuel/air equivalence ratios from 0.6 to 1.6 and temperatures from 1500 to 2050 K. Measurements were obtained spanning rotational quantum numbers from 4.5 to 16.5. The collision induced frequency shift was determined to be 0.1 that of the collisional broadening.
TL;DR: In this paper, the Holstein radiation-trapping equation was solved numerically for cylindrically and spherically symmetric geometries, and analytical fitting equations for the trapping factors and for the shapes of the 10 lowest-order modes were given.
Abstract: We solve the Holstein radiation-trapping equation numerically for cylindrically and spherically symmetric geometries. For Doppler and Lorentz lineshapes, we give analytical fitting equations for the trapping factors and for the shapes of the 10 lowest-order modes. For Voigt profiles, we modify the classical Walsh-interpolation formula so that it is now applicable at all opacities and for all modes. The results are checked by Monte Carlo simulation and by comparison with existing approximations. Our fits and interpolations yield 2–20% accuracy.
TL;DR: In this paper, a new radiative transfer theory is developed for stochastically inhomogeneous scattering media, where the three-dimensional shapes and large scale structures of the media are modeled by stochastic interfaces separating regions of different scattering properties.
Abstract: New radiative transfer theory is developed for stochastically inhomogeneous scattering media. The three-dimensional shapes and large scale (compared to the mean free path) structures of the media are modeled by stochastic interfaces separating regions of different scattering properties. The small scale fluctuations are characterized by a pair-correlation function. The radiative transfer equation is extended to include individual scattering and propagation probabilities of a ray for each subregion as well as the probability for a ray to cross the interface between two subregions. The propagation probability is found to depend on the entire preceding path of the ray; the present formulation accounts for the two previous scatterings. A new adding/doubling algorithm is developed to solve this problem numerically. Transmission through a cloud layer and backward scattering seem to be particularly sensitive to inhomogeneities.
TL;DR: In this article, the role of the Al2O3 particles from a highly loaded solid propellant (up to 16% in weight) on the plume radiation of a small rocket motor (5 cm in diameter) was investigated.
Abstract: Solid propellant rocket motors can achieve high specific impulse with metal fuel additives such as aluminum. Combustion of aluminum produces condensed alumina particles. Besides causing performance losses in the nozzle, the condensed Al2O3 particles are the major source of primary smoke in the exhaust plume. The particulate matter can also have major effects upon the plume i.r. signature. High number densities of particles can block gas-phase radiation from the plume. They can also be the source of radiation, especially the larger particles which exit the nozzle not in thermal equilibrium with the gas. In the past, the expected effects of particle size on the plume i.r. signature have been determined almost exclusively from predictions made with flow and radiation codes. The aim of the present work was to investigate the role of the Al/Al2O3 particles from a highly loaded solid propellant (up to 16% in weight) on the plume radiation of a small rocket motor (5 cm in diameter). The spatial variation of particle size distribution was simultaneously measured with the overall radiation of a portion of the plume in the i.r. band (3.5–5.0 μ). In micro-motors, operating with highly aluminized solid propellant, the condensed particles in the near exhaust plume were the major source of radiation in the 3.5–5 μ wavelength band. Motors with longer residence time and operating at medium chamber pressures produced more particles in the micron sized range. The role of afterburning was predominately confined to reheating of the alumina particles to a higher temperature, at which the condensed Al2O3 radiated more than gaseous species. Even with 30% Al2O3 in the plume, the plume of small motors can be considered as approximately conical in shape, with volume distributed radiating sources. Motor conditions producing larger particles in the plume core were thus found to increase plume radiation from that region. The overall apparent emissivity of the plume was between 0.15 and 0.25 (dominantly 0.16–0.19). Nearfield particle size distributions were tri- or quadra-modal and the farfield contained significantly fewer large particles. Thus, assumed monomodal distributions should not be expected to result in the correct prediction of the effects of particles onplume signature, nor can particle size data obtained in the farfield be expected to be applicable in the nearfield.
TL;DR: In this paper, a solution for the PN method for multi-group radiative transfer in a homogeneous plane-parallel medium that contains group sources that vary with position and direction is presented.
Abstract: The spherical-harmonics method, also called the PN method, is used to develop solutions to a class of multi-group or non-gray radiation transport problems. The multi- group model considered allows an anisotropic scattering law and transfer from any group to any group. In addition to a spherical-harmonics solution for the case of a homogeneous radiative-transfer equation, a particular solution for the PN method is derived for the case of multi-group radiative transfer in a homogeneous plane-parallel medium that contains group sources that vary with position and direction. Computational aspects of the developed solutions are discussed, and numerical results for a test case are reported.
TL;DR: In this article, the integrated band intensities of the ν9 and ν11 bands of N2O4 were measured around 1757 and 1261 cm-1, respectively.
Abstract: We have measured the integrated band intensities of the ν9 and ν11 bands of N2O4 which are observed around 1757 and 1261 cm-1, respectively. By varying temperature and pressure, we have obtained: Sband(ν9) = 9.60(130), 9.10(24), 8.80(66) and Sband(ν11)= 5.93(64), 5.70(21) and 5.33(46) (in 10-17 cm/molecule) at 293.15 (60), 277.25 (60) and 261.65 (60) K, respectively.
TL;DR: In this article, a theoretical analysis of the absorption coefficient at 153 GHz was presented for pure water vapor and water vapor-nitrogen mixtures, which is 30 GHz lower than the resonant frequency of the nearest strong water line (183 GHz) and complements previous measurements at 213 GHz.
Abstract: New experimental data on and a theoretical analysis of the absorption coefficient at 153 GHz are presented for pure water vapor and water vapor-nitrogen mixtures. This frequency is 30 GHz lower than the resonant frequency of the nearest strong water line (183 GHz) and complements our previous measurements at 213 GHz. The pressure dependence is observed to be quadratic in the case of pure water vapor, while in the case of mixtures there are both linear and quadratic density components. By fitting our experimental data taken at several temperatures we have obtained the temperature dependence of the absorption. Our experimental data are compared to several theoretical models with and without a continuum contribution, and we find that none of the models is in very good agreement with the data; in the case of pure water vapor, the continuum contribution calculated using the recent theoretical absorption gives the best results. In general, the agreement between the data and the various models is less satisfactory than found previously in the high-frequency wing. The anisotropy in the observed absorption differs from that currently used in atmospheric models.
TL;DR: In this article, the absolute intensities and foreign gas broadening coefficients of the 18 0,18 ←18 1,18 and 11 1,10 ←11 2,10 transitions in the v 7 band of C 2 H 4 near 948 cm -1 have been measured at a spectral resolution of ∽5 × 10 -4 cm −1 using tunable diode laser spectrometry.
Abstract: Absolute intensities and foreign gas broadening coefficients of the 18 0,18 ←18 1,18 and 11 1,10 ←11 2,10 transitions in the v 7 band of C 2 H 4 near 948 cm -1 have been measured at a spectral resolution of ∽5 × 10 -4 cm -1 using tunable diode laser spectrometry. Ar, He, N 2 , and O 2 were used as the broadening gases. In order to determine the temperature dependence of the broadening coefficient, data were obtained at temperatures ranging from 150 to 296 K. The absolute intensity of the 5 0,5 ←5 1,5 transition was also found at 296 K. A band strength of 339 ± 10 cm -2 atm -1 was obtained from weighted averages of the individual line intensities and a rigid asymmetric top calculation.
TL;DR: In this paper, electron number density and kinetic temperature values were inferred from the Stark- and Doppler-broadening components of the absorption lineshapes, respectively, in an atmospheric pressure, 1.4- kW, 27-MHz inductively coupled argon-oxygen (12% O2/argon) plasma.
Abstract: Narrow-bandwidth semiconductor (GaAlAs) lasers have been used to record spectrally resolved atomic oxygen (7772 A) and argon (8425 A) lineshapes, corresponding to the 3s5S02→3p5P3 and 4s3P1→4p3D2 transitions, in an atmospheric pressure, 1.4- kW, 27-MHz inductively coupled argon-oxygen (12% O2/argon) plasma. Electron number density and kinetic temperature values were inferred from the Stark- and Doppler-broadening components of the absorption lineshapes, respectively. The ionization temperature was calculated from the measured electron number density assuming ionization (Saha) equilibrium. Values of excited- state species number density and population temperature were determined from the frequency- integrated absorption coefficient for each transition. The difference between the ionization and population temperatures reflects the presence of a suprathermal electron number density in the flowfield. In addition, the excellent agreement between the kinetic and population temperatures suggests that the population in the oxygen and argon lowest excited states may be described by a Boltzmann distribution at the kinetic temperature. The methods presented extend effectively the range of semiconductor-laser diagnostics to mixed-gas plasmas and flowfields containing atomic oxygen.