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Abstract: Pressure broadened (1atm. ) absorption cross sections and integrated band intensities have been derived from laboratory spectra of , recorded at 276, 298, and 323K, covering 600–. The spectra were recorded at a resolution of using a commercial Fourier transform spectrometer and a custom flowing sample delivery system. We report integrated absorption cross sections for intervals corresponding to the most prominent bands, compare the results with previously reported values, and discuss error sources, which are estimated as with systematic error the largest error source. [Copyright &y& Elsevier]

Several new infrared absorption bands for 32S16O3 have been measured and analyzed. The principal bands observed were ν1+ν2 (at 1561 cm-1), ν1+ν4 (at 1594 cm-1), ν3+ν4 (at 1918 cm-1), and 3ν3 (at 4136 cm-1). Except for 3ν3, these bands are very complicated because of (a) the Coriolis coupling between ν2 and ν4, (b) the Fermi resonance between ν1 and 2ν4, (c) the Fermi resonance between ν1 and 2ν2, (d) ordinary l-type resonance that couples levels that differ by 2 in both the k and l quantum numbers, and (e) the vibrational l-type resonance between the A1′ and A2′ levels of ν3+ν4. The unraveling of the complex pattern of these bands was facilitated by a systematic approach to the understanding of the various interactions. Fortunately, previous work on the fundamentals permitted good estimates of many constants necessary to begin the assignments and the fit of the measurements. In addition, the use of hot band transitions accompanying the ν3 band was an essential aid in fitting the ν3+ν4 transitions since these could be directly observed for only one of four interacting states. From the hot band analysis we find that the A1′ vibrational level is 3.50 cm-1 above the A2′ level, i.e., r34=1.75236(7) cm-1. In the case of the 3ν3 band, the spectral analysis is straightforward and a weak Δk=±2, Δl3=±2 interaction between the l3=1 and l3=3 substates locates the latter A1′ and A2′ “ghost” states 22.55(4) cm-1 higher than the infrared accessible l3=1 E′ state. [Copyright &y& Elsevier]

A Bruker IFS-120HR Fourier transform spectrometer located at the Pacific Northwest National Laboratory (PNNL) in Richland, Washington was used to record a series of spectra of pure H 2 O and air-broadened H 2 O in the regions of the ν 1 and ν 3 bands (3450–4000 cm −1 ) at different pressures, temperatures and volume mixing ratios of H 2 O in air. Eighteen high-resolution, high signal-to-noise (S/N) ratio absorption spectra were recorded at T = 268, 296 and 353 K using two temperature-controlled absorption cells with path lengths of 9.906(1) and 19.95(1) cm. The resolution of the spectra recorded with the 9.906 cm and 19.95 cm absorption cells was 0.006 and 0.008 cm −1 , respectively. A multispectrum nonlinear least squares fitting technique was employed to fit all the eighteen spectra simultaneously to retrieve 313 accurate line positions, 315 intensities, 229 Lorentz air-broadened half-width and 213 air-shift coefficients and their temperature dependences (136 for air-broadened width and 128 for air-shift coefficients, respectively). Room temperature self-broadened half-width coefficients for 209 transitions and self-shift coefficients for 106 transitions were also measured. Line mixing coefficients were experimentally determined for isolated sets of 10 transition pairs for H 2 O-air and 8 transition pairs for H 2 O-H 2 O using the off-diagonal relaxation matrix element formalism, and 85 quadratic speed dependence parameters were measured. Modified Complex Robert-Bonamy (MCRB) calculations of self-, and air-broadened (from N 2 - and O 2 -broadening) half-width and air-shift coefficients, and temperature dependence exponents of air-broadened half-width coefficients are made. The measurements and calculations are compared with each other and with similar parameters reported in the literature. [ABSTRACT FROM AUTHOR]

We report experimental measurements of spectral line shape parameters (air-broadened width, shift, and line mixing coefficients) for several transitions in the ν 3 Q branch of methane in the 3000–3023 cm −1 region. 13 high-resolution, room temperature laboratory spectra of pure methane and air-broadened methane recorded with two different Fourier transform spectrometers are fitted. 12 of these spectra were acquired at 0.01 cm −1 resolution with the McMath-Pierce FTS at the National Solar Observatory on Kitt Peak, and one higher-resolution (∼0.0011 cm −1 ) low pressure methane spectrum was obtained with the Bruker IFS-120HR FTS at the Pacific Northwest National Laboratory, in Richland, Washington. All the spectra were obtained using high purity natural samples of CH 4 and lean mixtures of the same natural CH 4 in dry air. For the 12 spectra recorded at Kitt Peak, three different absorption cells (L = 5, 25 and 150 cm) were used while the methane spectrum at PNNL was obtained using a 19.95 cm long absorption cell. For the analysis, an interactive multispectrum nonlinear least squares fitting software was employed where all the 13 spectra were fitted simultaneously. An accurate and self-consistent set of line parameters were determined by constraining a few of those for severely blended transitions. Line mixing was measured for 14 transition pairs for the CH 4 -air collision system. A constant speed dependence parameter, consistent with measured speed dependence values obtained in other methane bands, was applied to all the transitions included in the fitted region. The present measurements are compared to values reported in the literature. [ABSTRACT FROM AUTHOR]