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We report revisited experimentally retrieved and theoretically calculated He-broadened Lorentz half-width coefficients and He- pressure-shift coefficients of 45 carbon monoxide transitions in the 1←0 band. The spectra analyzed in this study were recorded over a range of temperatures between 79 and 296 K. The He-broadened line parameters and their temperature dependences were retrieved using a multispectrum nonlinear least squares analysis program. The line shape models used in this study include Voigt, speed dependent Voigt, Rautian (to take into account confinement narrowing) and Rautian with speed dependence, all with an asymmetric component added to account for weak line mixing effects. We were unable to retrieve the temperature dependence of line mixing coefficients. A classical method was used to determine the He-narrowing parameters while quantum dynamical calculations were performed to determine He-broadening and He-pressure shifts coefficients at different temperatures. The line mixing coefficients were also derived from the exponential power gap law and the energy corrected sudden approximation. The current measurements and theoretical results are compared with other published results, where appropriate. [ABSTRACT FROM AUTHOR]

This paper presents the results of a spectroscopic line shape study of self- and nitrogen-broadened 12 CH 3 D transitions in the ν 3 and ν 5 bands in the Triad region. We combined five pure gas spectra with eighteen spectra of lean mixtures of 12 CH 3 D and nitrogen, all recorded with a Bruker IFS-125 HR Fourier transform spectrometer. The spectra have been analyzed simultaneously using a multispectrum nonlinear least squares fitting technique. N 2 -broadened line parameters for 184 transitions in the ν 3 band and 205 transitions in the ν 5 band were measured. In addition, line positions and line intensities were measured for 168 transitions in the ν 3 band and 214 transitions in the ν 5 band. We have observed 10 instances of weak line mixing corresponding to K ″=3 A1 or A2 transitions. Comparisons were made for the N 2 -broadening coefficients and associated temperature exponents with corresponding values calculated using a semi-classical Robert Bonamy type formalism that involved an inter-molecular potential with terms corresponding to short- and long-range interactions, and exact classical molecular trajectories. The theoretical N 2 -broadened coefficients are overestimated for high J values, but are in good agreement with the experimental values for small and middle range J values. [ABSTRACT FROM AUTHOR]

The temperature-dependences of line broadening and shift parameters for many 12 CH 3 D transitions have been determined using six high-resolution, high signal-to-noise ratio, room-temperature CH 3 D (98% purity) and CH 3 D-N 2 spectra recorded with 25 cm path length ( at 0.01 cm −1 unapodized resolution) using the McMath−Pierce FTS located on Kitt Peak, Arizona, and 17 additional high quality, pure CH 3 D (99% purity) and CH 3 D-N 2 spectra recorded between 79 and 296 K with the 20.38 cm path coolable cell (at 0.0056 cm −1 unapodized resolution) with the Bruker 125HR FTS at the Jet Propulsion Laboratory (JPL), Pasadena, California. The spectra have been fitted simultaneously applying a multispectrum nonlinear least-squares technique. In the analysis, the Lorentzian N 2 -broadened half-width coefficients and the corresponding pressure-shift coefficients as well as their temperature dependences are extracted for about 400 transitions (0≤ J ″≤19, K ″≤16) in the perpendicular (Δ K =±1) ν 6 band. At 296 K, the measured N 2 -broadened half-width coefficients range from 0.0209 to 0.0782 cm −1 atm −1 whereas the majority of the associated N 2 -induced shift coefficients are negative, and the values are between -0.016 and 0.005 cm −1 atm −1 . The temperature dependence exponents for N 2 -broadened half-widths range between 0.264 and 0.924, whereas the temperature dependence coefficients for N 2 -induced shifts are between 0 and 0.00011 cm −1 atm −1 K −1 . The N 2 -broadened half-width coefficients have been also calculated using a semi-classical approach based on a rigorous treatment of the active molecule as a symmetric top, a model intermolecular potential comprising both short- and long-range interactions, and exact classical trajectories. The role of the various high-order multipoles in the line-broadening at low, middle and high values of the rotational quantum number J ″ has been investigated and the main features of the K -dependences analyzed. The calculations performed for 296, 240 and 190 K have allowed to deduce the half-width temperature-dependence exponents, completing the general comparison of our new experimental results with those which are available in the literature. [ABSTRACT FROM AUTHOR]

We have constructed a stabilized low temperature infrared absorption cell cooled by an open cycle refrigerator, which can run with liquid nitrogen from 250 to 80 K or with liquid helium from 80 K to a few kelvin. Several CO infrared spectra were recorded at low temperature using a tunable diode laser spectrometer. These spectra were analyzed taking into account the detailed effects of collisions on the line profile when the pressure increases. We also recorded spectra at very low pressure to accurately model the diode laser emission. Spectra of the R(2) line in the fundamental band of 13CO cooled by collisions with helium buffer gas at 10.5 K and at pressures near 1 Torr have been recorded. The He-pressure broadening parameter (γ0=0.3 cm-1 atm-1) has been derived from the simultaneous analysis of four spectra at different pressures. [Copyright &y& Elsevier]

Self- and hydrogen-broadening coefficients and pressure-shift coefficients for the first overtone band transitions of 12C16O at room temperature have been determined through analysis of nine high-resolution (0.0055 cm−1) absorption spectra. These spectra were recorded using the 1-m Fourier transform spectrometer (FTS) at the McMath-Pierce facility of the National Solar Observatory on Kitt Peak, Arizona. Because of the short path length of the sample cell (10.0 cm), the volume mixing ratios of CO in hydrogen were relatively high, ∼18–22%, to achieve measurable absorption. These large volume-mixing ratios necessitated the simultaneous determination of the CO self-broadening and self-shift coefficients along with the hydrogen-broadening and hydrogen-induced shift coefficients. We have determined these coefficients at room temperature, along with line positions and absolute intensities, for the P(27) through R(27) 12C16O 2-0 transitions by fitting the entire spectral interval from 4130 to 4345 cm−1 in all nine spectra simultaneously using our multispectrum nonlinear least-squares procedure. Our intensity measurements are consistently low (1–6%) compared with the HITRAN values but the majority of the intensities are within 4% of the HITRAN values. The values of self-broadening coefficients vary from 0.0452 to 0.0862 cm−1 atm−1 at 296 K and those of hydrogen-broadening coefficient range between 0.0475 and 0.0795 cm−1 atm−1 at 296 K. All of our measured self- and hydrogen-shift coefficients are negative and range from −0.002 to −0.008 cm−1 atm−1. With the pressure and path length used in our study we did not find evidence of significant line mixing in either the self- or hydrogen-broadened spectra. This study represents the first high-resolution experimental determination of hydrogen-induced pressure broadening and pressure-shift coefficients in the 2-0 band of 12C16O at room temperature. [Copyright &y& Elsevier]