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Lorentz half-width coefficients and their temperature dependence exponents for CO 2 broadening in the fundamental bands of HDO are important for reliable and accurate interpretation of Mars and Venus atmospheric data and to determine D/H. Uncertainties in the temperature dependences of the CO 2 -broadened half-width coefficients lead to large errors in the retrieved mixing ratios and hence in HDO column abundances. In this high-resolution FTIR laboratory study, we report first measurements of the temperature dependences of half-width coefficients for HDO transitions in the ν 1 and 2ν 2 bands broadened by CO 2 . Accurate line positions, intensities, CO 2 -broadened width and pressure shift coefficients, their temperature dependences, collisional line mixing coefficients for HDO-CO 2 system and quadratic speed dependence parameters have been retrieved for a large number of transitions in the ν 1 band. Room-temperature self-broadened half-width coefficients, self-shift coefficients, and collisional line-mixing coefficients for HDO-HDO system were also measured for the same number of ν 1 transitions. Positions and intensities were measured for nearly 60 transitions in the weaker 2ν 2 band along with a few room-temperature measurements of CO 2 - and self-broadening and pressure-shift coefficients. These results were obtained from simultaneous nonlinear least squares fittings of ten high-resolution absorption spectra recorded with the Bruker IFS-125HR FTS at JPL and two coolable sample cells. Modified Complex Robert-Bonamy (MCRB) formalism was applied to compute both types of broadening and pressure shift coefficients, and the temperature dependences of the CO 2 - and self-broadening parameters. Present measurements are compared with the MCRB calculations and other theoretical values reported in the literature. [ABSTRACT FROM AUTHOR]

This study reports the results from analyzing a number of high resolution, high signal-to-noise ratio (S/N) spectra in the 2.06-μm spectral region for pure CO 2 and mixtures of CO 2 in dry air. A multispectrum nonlinear least squares curve fitting technique has been used to retrieve the various spectral line parameters. The dataset includes 27 spectra: ten pure CO 2 , two 99% 13 C-enriched CO 2 and fifteen spectra of mixtures of 12 C-enriched CO 2 in dry air. The spectra were recorded at various gas sample temperatures between 170 and 297 K. The absorption path lengths range from 0.347 to 49 m. The sample pressures for the pure CO 2 spectra varied from 1.1 to 594 Torr; for the two 13 CO 2 spectra the pressures were ∼10 and 146 Torr. For the air-broadened spectra, the pressures of the gas mixtures varied between 200 and 711 Torr with CO 2 volume mixing ratios ranging from 0.014% to 0.203%. The multispectrum fitting technique was applied to fit simultaneously all these spectra to retrieve consistent set of line positions, intensities, and line shape parameters including their temperature dependences; for this, the Voigt line shape was modified to include line mixing (via the relaxation matrix formalism) and quadratic speed dependence. The new results are compared to select published values, including recent ab initio calculations. These results are required to retrieve the column averaged dry air mole fraction ( X CO2 ) from space-based observations, such as the Orbiting Carbon Observatory-2 (OCO-2) satellite mission that NASA launched in July 2014. [ABSTRACT FROM AUTHOR]

Abstract: The first air broadening line shape parameters were determined for the 2←0 bands of 13C16O near 4166.8cm−1 and 12C18O near 4159.0cm−1. Air-broadened Lorentz half-width coefficients, their temperature dependence exponents; air-induced pressure shift coefficients, their temperature dependences; and air line mixing coefficients were measured. Additionally, speed-dependent line shapes with line mixing employing the off-diagonal relaxation matrix element coefficients were applied to minimize the fit residuals. Finally, individual line positions and line intensities of the two isotopologues were constrained to the well-known theoretical quantum mechanical expressions in order to obtain the rovibrational (G, B, D and H) and band intensity parameters (including Herman–Wallis coefficients). For this, laboratory spectra were recorded at 0.005cm−1 resolution using a temperature-controlled coolable absorption cell configured inside a Bruker IFS 125HR Fourier transform spectrometer. Gas temperatures and pressures for the spectra varied from 150 to 298K and 20 to 700Torr, respectively. Results were obtained from broad-band multispectrum least-squares fitting of the 4000–4360cm−1 spectral region. Four isotope-enriched pure sample spectra and twelve spectra with air+CO samples (13C16O or 12C18O, as appropriate) were fitted simultaneously. The results obtained for 13C16O and 12C18O are compared and discussed. [Copyright &y& Elsevier]

Abstract: Accurate values for line positions, absolute line intensities, self-broadened half width and self-pressure-induced shift coefficients have been measured for over 400 allowed and forbidden transitions in the ν4 band of methane (12CH4). Temperature dependences of half width and pressure-induced shift coefficients were also determined for many of these transitions. The spectra used in this study were recorded at temperatures between 210 and 314K using the National Solar Observatory''s 1m Fourier transform spectrometer at the McMath-Pierce solar telescope. The complete data set included 60 high-resolution (0.006–0.01cm−1) absorption spectra of pure methane and methane mixed with dry air. The analysis was performed using a multispectrum nonlinear least squares curve fitting technique where a number of spectra (20 or more) were fit simultaneously in spectral intervals 5–15cm−1 wide. In addition to the line broadening and shift parameters, line mixing coefficients (using the off-diagonal relaxation matrix element formalism) were determined for more than 50 A-, E-, and F-species transition pairs in J manifolds of the P- and R-branches. The measured self-broadened half width and self-shift coefficients, their temperature dependences and the line mixing parameters are compared to self-broadening results available in the literature and to air-broadened parameters determined for these transitions from the same set of spectra. [Copyright &y& Elsevier]

Abstract: Lorentz air-broadened half widths, pressure-induced shifts and their temperature dependences have been measured for over 430 transitions (allowed and forbidden) in the ν 4 band of 12CH4 over the temperature range 210–314K. A multispectrum non linear least squares fitting technique was used to simultaneously fit a large number of high-resolution (0.006–0.01cm−1) absorption spectra of pure methane and mixtures of methane diluted with dry air. Line mixing was detected for pairs of A-, E-, and F-species transitions in the P- and R-branch manifolds and quantified using the off-diagonal relaxation matrix elements formalism. The measured parameters are compared to air- and N2-broadened values reported in the literature for the ν 4 and other bands. The dependence of the various spectral line parameters upon the tetrahedral symmetry species and rotational quantum numbers of the transitions is discussed. All data used in the present work were recorded using the McMath–Pierce Fourier transform spectrometer located at the National Solar Observatory on Kitt Peak. [Copyright &y& Elsevier]

We report the first extensive experimental measurements of Ar-broadened half-width and pressure-induced shift coefficients, speed dependence parameters, and line mixing coefficients for the 30013←00001 and 30012←00001 bands of 16O12C16O centered near 6227 and 6348 cm–1, respectively. These parameters were determined from 15 self-broadened and six Ar-broadened CO2 spectra recorded at room temperature with long absorption path lengths (25 to 121 m) using the McMath–Pierce Fourier transform spectrometer (FTS) at the National Solar Observatory. All 21 spectra were fit simultaneously using a multispectrum nonlinear least-squares technique. The line positions and line intensities were constrained to quantum mechanical expressions to obtain maximum accuracies in the retrieved parameters. Speed-dependent line shapes with line mixing (via the relaxation matrix formalism) were required to remove systematic errors in the fit residuals using only the Voigt profile. Remaining fit residuals were minimized by adjusting the half-width and pressure-induced shift coefficients of the overlapping 31113←01101 and 31112←01101 hot bands. We compare the Ar-broadening parameters with those recently determined for self- and air-broadening in the 30012←00001 and 30013←00001 bands and also with other Ar-broadening values from the literature, as appropriate. [ABSTRACT FROM AUTHOR]

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High-resolution (0.005 cm-1) infrared absorption spectra of HCN in the 2ν2 band region near 1411 cm-1 have been recorded at room temperature using the Bruker IFS120HR Fourier transform spectrometer located at Pacific Northwest National Laboratory. Four spectra of high-purity (99.8%) HCN together with three spectra of lean mixtures (∼3%) of HCN in dry air were simultaneously fit using a multispectrum nonlinear least-squares procedure. The analysis yielded room temperature values for absolute intensities, self- and air-broadening coefficients, and self- and air-induced pressure shift coefficients for numerous lines in the 2ν20 band of H12C14N. In addition, intensities, self- and air-broadening coefficients for several lines of the 3ν21-ν21 hot band, as well as intensities for a number of lines in the 2ν20 band of H13C14N, were also determined. Since there are no previous measurements of broadening and shift parameters reported in the 2ν20 band, our results are compared with values recently determined in the ν1 band of H12C14N and with current HITRAN values. [Copyright &y& Elsevier]