Marie-Yvonne Perrin

Accurate calculated tabulations of IR and Raman CO 2 line broadening by CO 2 , H 2 O, N 2 , O 2 in the 300–2400-K temperature range

Pressure-broadening coefficients for (12)C(16)O(2) lines have been calculated with a recent model derived from the Robert and Bonamy approach which leads to more accurate results than the previously used Anderson-Tsao- Curnutte model. Systematic calculations of CO(2)-CO(2), CO(2)-H(2)O, CO(2)-N(2), and CO(2)-O(2) broadening coefficients in the 300-2400-K temperature range are presented. The results are suitable for both IR and Raman lines and should be useful for spectra calculations. Tabulations of the broadening coefficients are given together with simple analytical expressions for their rotational quantum number and temperature dependences.

Nonequilibrium vibrational kinetics of carbon monoxide at high translational mode temperatures

Abstract Recent experiments and analyses involving vibration-to-vibration (VV) pumped carbon monoxide are presented. Pure CO, and COAr mixtures, in a flowing-gas cell, are vibrationally excited by absorption of CO laser radiation. The pump laser is a slow-flow liquid-nitrogen wall-cooled device, which can be operated in either Q -switched or cw mode for these experiments. There is output down to the v =1−0 vibrational transition ( Q -switched) or v =2−1 (cw). CO has been VV pumped in these experiments to very high vibrational quantum levels, at partial pressures up to 65 Torr. The rotational/translational mode temperature has been measured by emission spectroscopy of rotationally resolved Swan bands of C 2 formed from reaction of the VV pumped CO. Measured rotational mode temperatures up to 1500 K have been achieved with strong VV pumping. Low levels of ionization have been observed under these extreme pumping conditions. Results of time-resolved experiments exploring the kinetics are presented. These results are analyzed using a time-dependent kinetic master equation modeling code for the vibrational state kinetics.

Accurate calculated tabulations of CO line broadening by H 2 O, N 2 , O 2 , and CO 2 in the 200–3000-K temperature range

We present accurate calculations of CO line-broadening coefficients. They have been calculated with a modelwhich has been tested with success on the broadening of CO,-; CO2 and H2O (Refs. 2,9,10) lines. A similar data base for broadening coefficients has already been made for CO2. The following results are presented as in Ref. 11. The broadening coefficients γ‌ m‌ of CO RJ=m-1 lines by H2O, CO2, N2, and O2 have been calculated in the 300-2400K range. The data of Refs. 7,6,4, and 12 have been used for CO-H2O, -CO2, -N2, and -O2, respectively. For a given value of the rotational quantum number m, calculations have only been made for temperatures >Tmin(m), where

Collisional broadening of CO2 IR lines. II. Calculations

The ability of available theoretical models in describing broadening mechanisms is tested for the CO2–O2, CO2–CO2, and CO2–N2 systems. It is shown that the Anderson–Tsao–Curnutte theory is inaccurate since short‐range forces can contribute significantly to broadening. We use the approach of Robert and Bonamy, but the usual expansion of the atom–atom potential to the fourth order around the intermolecular distance appears insufficient at short distances for these particular systems. We propose a better representation of the radial dependence of the atom–atom potential, while keeping the previous analytical expression of the cross section. Satisfactory results are obtained for both the rotational quantum number dependence of room‐temperature CO2–O2, CO2–CO2, and CO2–N2 half‐widths and the evolution of CO2–N2 broadening with temperature. It is shown that the isotropic part of the potential involved in the trajectory calculation must be coherently deduced from the atom–atom interaction potential.

AIR MIXTURE RADIATIVE PROPERTY MODELLING IN THE TEMPERATURE RANGE 10,000-40,000 K

Abstract A model based on the distribution functions of the absorption coefficients is used to describe the radiative properties of an air plasma at atmospheric pressure between 10,000 and 40,000 K. In order to account for spectral fine structure effects on radiative transfer in nonuniform media, fictitious species whose spectra reasonably satisfy the scaling approximation are introduced. The absorption spectra of these fictitious species are assumed to be spectrally uncorrelated. Radiative properties are described in terms of absorption coefficients and the model can be used with arbitrary radiative transfer equation solvers. Model parameters are generated from spectral high resolution calculations. The different approximations required to implement the model are discussed and their validity is checked by comparisons with line-by-line benchmarks. It is shown that the model can predict radiative transfer along strongly nonisothermal columns within a few percent.

Contributions of diatomic molecular electronic systems to heated air radiation

Abstract A spectroscopic database has been constructed for all the contributing electronic systems of air diatomic molecules for elevated temperatures (up to 15,000 K ). The electronic systems which have been investigated are N2 first- and second-positive, Birge–Hopfield 1 and 2, Carroll–Yoshino, Worley and Worley–Jenkins, N2+ Meinel, first- and second-negative, O2 Schumann–Runge and NO γ,β,δ,e,γ′,β′,11,000 A and infrared. The RKR potentials have been reconstructed in order to calculate the vibrational wavefunctions, and the electronic-vibrational part of line intensities has been computed with up-to-date ab-initio electronic transition moment functions. The results of our calculated vibrational band strengths are in good agreement with the available measurements. The positions and intensities of the rotational lines have been determined in intermediate a/b Hunds coupling case with up-to-date molecular constants, and the lambda doubling has been resolved when related parameters were available in the literature. Absorption spectra and the optically thin radiation source strengths of the studied electronic systems are presented and discussed in terms of their comparative contribution to emission and absorption.

Radiative transfer in LTE air plasmas for temperatures up to 15,000 K

Abstract Radiative transfer in local thermodynamic and chemical equilibrium N2–O2 plasmas is analyzed in this study using a line-by-line approach. The contributions of line absorption by atoms, ions and of continuous absorption by atoms, ions and molecules to the absorption coefficient of heated air are calculated. These data combined to our previous work on the contribution of molecular electronic systems to heated air radiation (J. Quant. Spectrosc. Radiat. Transfer 72 (2002) 503) lead to a reliable and exhaustive spectroscopic data base for radiative transfer in air plasmas and for temperatures up to 15,000 K . Line-by-line radiative transfer calculations are carried out for a simple planar geometry with prescribed temperature profiles. The spectral distribution of radiative fluxes and volumetric powers is analyzed and the relative contributions of continuum and line radiation are discussed.

Transfer of vibrational energy to electronic excited states and vibration enhanced carbon production in optically excited V−V pumped CO

Abstract CO in helium/argon mixtures are vibrationally excited by absorption of CO laser photons in a specially designed flowing gas cell. High vibrational levels (up to ν = 41) become populated by vibration-to-vibration transfer. Vibrational populations of the CO ground state are obtained by fitting the first overtone emission spectra. Transfer of vibrational energy to electronic excited states as well as vibration enhanced carbon production are studied. The CO ( A 1 Π − X 1 Σ + ) and the CO (b3Σ+−a3Π) emissions have been observed as well as atomic carbon lines. Several systems of C2 have been observed, of which the (d3Πg−a3Πu) Swan system is the most intense. Quenching of high vibrational levels of the CO ground state significantly decreases the emissions from the electronic excited states of CO and C2, indicating that their formation strongly depends on the vibrational excitation in the ground state. Formation mechanisms for these states are investigated.

Spectroscopic study of microwave plasmas of CO2 and CO2?N2 mixtures at atmospheric pressure

A comprehensive study of CO2 and CO2(97%)–N2(3%) plasmas produced by a microwave torch at atmospheric pressure is carried out through the spectroscopic analysis of Abel inverted emission spectra. The temperature profiles at the exit of the cavity are determined from oxygen and carbon atomic line absolute intensities and from the adjustment of vibration–rotation molecular spectra. The predominant molecular radiation in the UV and visible ranges emanates from the C2 Swan system in the case of CO2 plasma and from CN violet and red systems for CO2–N2 plasma. Significant contributions are also found from some O2, CO+ and NO systems. A sensitivity analysis to rotational and vibrational temperatures is carried out systematically for the different investigated spectral ranges. It is found that the various molecular temperatures are very close to each other. However, atomic temperatures are slightly lower than molecular ones, indicating a weak departure from thermodynamic or chemical equilibrium for atoms.

A unified nonequilibrium model for hypersonic flows

Kinetic theory is applied to a mixture of monoatomic and diatomic molecules in order to derive the macroscopic equation corresponding to the relaxation of vibrational energy. Diatomic molecules are described using the harmonic oscillator model. The SSH theory is extended and applied to evaluate the vibrational energy relaxation times which govern the process. The theoretical expressions are used to calculate the relaxation times of the main diatomic species in air: oxygen and nitrogen. These relaxation times are in good agreement with available experimental data. A comparison with previous models is then carried out. The coupled thermodynamic and chemical relaxation occurring after a strong normal shock wave in a one‐dimensional Eulerian flow is then studied. The computed results illustrate the interactions between three different phenomena: nonequilibrium thermodynamics, nonequilibrium chemistry, and dynamics of the flow. A complete analysis of these interactions is provided, and the influence of thermod...