J.M. Hartmann

Validity of band-model calculations for CO2 and H2O applied to radiative properties and conductive-radiative transfer

Abstract A previously presented line-by-line (LBL) calculation is used to test the validity of various approximate models. Narrow-band model parameters are generated from the lines used by the LBL approach in the 150–8000 cm -1 and 300–1500 K ranges. The accuracy of narrow-band models and of approximations for nonuniform paths applied to transmissivities and intensities of columns is studied. Random-statistical models give good results for the transmissivities but inaccurate results for the emitted intensities. Applications to combined conductive-radiative transfer in one-dimensional media are then presented. The temperature and flux distributions predicted by wide-band models are accurate when radiative transfer is preponderant; narrow-band models must be used in the case of optically thin media (e.g. in boundary layers).

Temperature-dependent measurements and modeling of absorption by CO2-N2 mixtures in the far line-wings of the 4.3μm CO2 band

Author Institution: Laboratoire E.M.2.C du CNRS (UPR 73) et de lEcole Centrale des Arts et Manufactures, Ecole Centrale, Grande voie des Vignes

Line-by-line and narrow-band statistical model calculations for H2O

Abstract In line-by-line calculations we use hot-band lines generated from the AFGL or GEISA data. The parameters of a random statistical model are calculated from these lines for 25 cm -1 wide intervals. Comparisons are made between experimental spectra and results of the two theoretical models for the 1595 and 3755 cm -1 bands between 900 and 1500 K. The validities of the statistical model and of the Curtis-Godson and Lindquist-Simmons approximations for nonisothermal and inhomogeneous media are tested.

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.

Calculated tabulations of H 2 O line broadening by H 2 O, N 2 , O 2 , and CO 2 at high temperature

We present calculations of the temperature dependence of H(2)O pressure broadening parameters by H(2)O, CO(2), N(2), and O(2). They were made for Q-lines with a theoretical model which provides a correct treatment of close collisions and has been widely tested. The results should be useful for Raman spectra calculations. A simple law is proposed to deduce halfwidths of P- and R-lines from the Q-line results. The accuracy of this law at high temperature is demonstrated. A simple analytical representation of a constant halfwidth approximation is also given.

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.

Temperature and perturber dependences of water vapor line-broadening. Experiments at 183 GHz; calculations below 1000 GHz

Measurements of linewidths of the 313 ← 220 H2O line at 183 GHz are presented. These include broadening by H2O, N2, O2, and Ar with the temperature dependence in the 300–390 K range. The room-temperature experiments are in good agreement with previous results. Systematic calculations of H2O line-broadening parameters of lines centered below 1000 GHz are also presented. These have been performed for a recently developed and successfully tested model. Tabulations of the room-temperature values and temperature dependence for self-, N2-, O2-, air-, and CO2-broadening are given. These data should be useful for spectral calculations required by atmospheric applications.

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 γu200c mu200c 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.

The infrared continuum of pure water vapor: Calculations and high-temperature measurements

Abstract We present experimental and theoretical studies of medium infrared absorption by pure water vapor. Measurements have been made in the 1900–2600 cm -1 and 3900–4600 cm -1 regions, for temperatures and pressures in the 500–900 K and 0–70 atm ranges, respectively. They are consistent with available data and enable the determination of continuum absorption parameters. It is shown that calculations with line shapes derived from the impact approximation are very inaccurate. Models accounting for the finite durations of collisions and line-mixing through wave-number dependent effective broadening parameters are introduced. The latter have been determined using two different approaches, which are (i) empirical determinations from fits of experimental data and (ii) direct predictions from first principles using a statistical approach. Effective broadening parameters obtained using these two different approaches are in satisfactory agreement for both the temperature and wavenumber dependencies. These data are tested by calculations of continua in various spectral regions and the agreement with measured values is satisfactory. The remaining discrepancies probably result from the influence of the internal structures of the absorption bands considered and thus from the influence of line-mixing. Nevertheless, accurate predictions are obtained in wide temperature and spectral ranges when the total absorption at elevated density is considered. This agreement, which is due to the relatively weak continuum absorption and large contributions of nearby lines, makes the present models suitable for most practical applications involving elevated densities.