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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]

Accurate knowledge of spectroscopic line parameters of PH3 is important for remote sensing of the outer planets, especially Jupiter and Saturn. In a recent study, line positions and intensities for the Pentad bands of PH3 have been reported from analysis of high-resolution, high signal-to noise room-temperature spectra recorded with two Fourier transform spectrometers (2014) [1]. The results presented in this study were obtained during the analysis of positions and intensities, but here we focus on the measurements of spectral line shapes (e.g. widths, shifts, line mixing) for the 2ν4, ν2 + ν4, ν1 and ν3 bands. A multispectrum nonlinear least squares curve fitting technique employing a non-Voigt line shape to include line mixing and speed dependence of the Lorentz width was employed to fit the spectra simultaneously. The least squares fittings were performed on five room-temperature spectra recorded at various PH3 pressures (~2-50 Torr) with the Bruker IFS-125HR Fourier transform spectrometer (FTS) located at the Pacific Northwest National Laboratory (PNNL), in Richland, Washington. Over 840 Lorentz self-broadened half-width coefficients, 620 self-shift coefficients and 185 speed dependence parameters were measured. Line mixing was detected for transitions in the 2ν4, ν1 and ν3 bands, and their values were quantified for 10 A+A- pairs of transitions via off-diagonal relaxation matrix element formalism. The dependences of the measured half-width coefficients on the J and K rotational quanta of the transitions are discussed. The self-width coefficients for the ν1 and ν3 bands from this study are compared to the self-width coefficients for transitions with the same rotational quanta (J, K) reported for the Dyad (ν2 and ν4) bands. The measurements from present study should be useful for the development of a reliable theoretical modeling of pressure-broadened widths, shifts and line mixing in symmetric top molecules with C3v symmetry in general, and of PH3 in particular. [ABSTRACT FROM AUTHOR]

Abstract: We describe atmospheric validation of and CO2 absorption coefficient databases for use by the Orbiting Carbon Observatory (OCO-2). The OCO-2 mission will collect the measurements needed to estimate column-averaged CO2 dry air mole fraction within 1ppm accuracy without the region- or airmass-dependent biases that would significantly degrade efforts to understand carbon sources and sinks on a global scale. To accomplish this, the forward radiative transfer model used to generate synthetic atmospheric spectra for retrievals must achieve unprecedented spectroscopic fidelity within the short wave infrared CO2 bands sampled by the sensors. The failure of Voigt line shapes and conventional line mixing formulations for such objectives has motivated significant revisions to line shape models used to generate the gas absorption cross sections for the OCO-2 forward model. In this paper, we test line mixing and speed dependent line shapes combined with improved experimental line parameters. We evaluate pre-computed absorption coefficients in the two spectral regions of CO2 absorbtion using high resolution FT-IR laboratory spectra, atmospheric spectra from the Total Carbon Column Observing Network (TCCON), and medium resolution soundings from the space-based Greenhouse Gases Observing Satellite (GOSAT). [Copyright &y& Elsevier]

Abstract: The McMath-Pierce Fourier transform spectrometer located at the National Solar Observatory (NSO) on Kitt Peak, Arizona, was used to record infrared high resolution absorption spectra of CO2 spectra broadened by O2. These spectra were analyzed to measure O2-broadened half-width coefficients, O2-induced pressure-shift coefficients and speed dependent parameters for transitions in the 30013←00001 and 30012←00001 bands of 16O12C16O located near 6227 and 6348cm−1, respectively. All spectra were obtained at room temperature using the long path, 6m base path White cell available at NSO. A multispectrum nonlinear least-squares fitting algorithm employing Voigt line shapes modified to include line mixing and speed dependence was used to fit simultaneously a total of 19 spectra in the 6120–6280cm−1 (30013←00001) and 6280–6395cm−1 (30012←00001) spectral regions. 16 of the 19 spectra analyzed in this work were self broadened and three spectra were lean mixtures of CO2 in O2. The volume mixing ratios of CO2 in the three spectra varied between 0.06 and 0.1. Lorentz half-width and pressure-induced shift coefficients were measured for all transitions in the P(50)–R(50) range in both vibrational bands. The results obtained from present analysis have been compared with measurements available in the literature for self-, air-, oxygen- and argon-broadening. No significant differences were observed between the broadening and shift coefficients of the two bands. The N2-broadened half-width and pressure-shift coefficients were computed from measured air- and O2-broadened width and shift coefficients. [ABSTRACT FROM AUTHOR]

Abstract: Absolute intensities, self- and air-broadening coefficients, self- and air-induced shift coefficients and their temperature dependences have been determined for lines belonging to the P- and R-branches of the ν2 band of H12C14N centered near 712cm−1. Infrared spectra of HCN in the 14-μm region were obtained at high resolution (0.002–0.008cm−1) using two different Fourier transform spectrometers (FTS), the McMath-Pierce FTS at the National Solar Observatory on Kitt Peak and the Bruker IFS 120HR FTS at the Pacific Northwest National Laboratory. Spectra were recorded with 99.8% pure HCN as well as lean mixtures of HCN in air at various temperatures ranging between +26 and −60°C. A multispectrum nonlinear least squares technique was used to fit selected intervals of 36 spectra simultaneously to obtain the line positions, intensities, broadening, and shift parameters. The measured line intensities were analyzed to determine the vibrational band intensity and the Herman–Wallis coefficients. The measured self-broadening coefficients vary between 0.2 and 1.2cm−1atm−1 at 296K, and the air-broadening coefficients range from 0.08 to 0.14cm−1atm−1 at 296K. The temperature dependence exponents of self-broadening range from 1.46 to −0.12 while the corresponding exponents for air broadening vary between 0.58 and 0.86. The present measurements are the first known determination of negative values for the temperature dependence exponents of HCN-broadening coefficients. We were able to support our self-broadening measurements with appropriate theoretical calculations. Our present measurements are compared, where possible, with previous measurements for this and other HCN bands, as well as the parameters that are included in the 2000 and 2004 editions of the high-resolution transmission (HITRAN) database. [Copyright &y& Elsevier]

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]

Extensive high-resolution experimental determination is provided for air- and N2-broadening and pressure shift coefficients for the two 13C16O2 laser bands (located at 913.4 and 1017.6 cm−1, respectively), in addition to new measurements of self-broadening and self-shift coefficients for the 12C16O2 laser bands. These parameters were determined from analysis of spectra recorded with the McMath–Pierce Fourier transform spectrometer (FTS) of the National Solar Observatory on Kitt Peak, Arizona. We used a multispectrum nonlinear least-squares fitting technique to analyze 30 long path, room temperature absorption spectra. By combining the spectra of 12CO2 and 13CO2 in the same fit we were able to obtain a consistent set of line parameters for both molecules. The results obtained for the 12CO2 and 13CO2 laser bands were compared with each other, with values in the HITRAN database, and with values reported in the literature for CO2 bands. Comparisons revealed no significant differences in the broadening or shift coefficients between the two laser bands. The coefficients determined for the two isotopomers agreed closely. [Copyright &y& Elsevier]

Line intensities of the two 12C16O2 laser bands (ν3–ν1 and ν3–2ν20) centered near 960.9 and 1063.7 cm−1, respectively, were obtained from analysis of 30 room temperature long path laboratory absorption spectra recorded at 0.0028 and 0.0053 cm−1 resolution with the McMath–Pierce Fourier transform spectrometer at the National Solar Observatory (located on Kitt Peak). The spectra were analyzed simultaneously with the multispectrum nonlinear least-squares fitting procedure. The measured line intensities were further analyzed to derive the vibrational band intensities and Herman–Wallis coefficients. [Copyright &y& Elsevier]

In this study we report the first high-resolution measurements of pressure broadening and pressure-induced shift coefficients due to nitrogen for rovibrational transitions in the ν3 band of 13C16O2. N2 broadening and shift coefficients of ν312C16O2 transitions were also measured. In addition, nitrogen-broadening coefficients for many transitions in the ν3+ν2−ν2 hot band of 13C16O2 as well as the ν3 band of 13C16O18O were also determined. The results were obtained by analyzing five high-resolution (0.0028 cm−1) room temperature laboratory absorption spectra with a multispectrum nonlinear least-squares spectral fitting technique. The data were recorded with the McMath-Pierce Fourier transform spectrometer of the National Solar Observatory on Kitt Peak using a 4.08 cm sample cell, total pressures up to 470 Torr, and a 90% 13C-enriched CO2 sample. For the pressure-broadened spectra the 13C16O2 volume-mixing ratios were⩽0.5%. Similar to broadening coefficients, the measured pressure shift coefficients were also found to be transition dependent. However, the shift coefficients were different in the P and R branch lines with the same rotational quantum number, J. The measured nitrogen-broadening coefficients range from 0.0960 to 0.0643 cm−1 atm−1 at 296 K. The measured shift coefficients were all negative and varied between 0 and −0.0036 cm−1 atm−1. The results obtained are compared with other values reported in the literature. [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]

Lorentz self- and nitrogen-broadening coefficients as well as self- and nitrogen-pressure induced shift coefficients were measured at room temperature for more than 440 transitions in the QP, QQ and QR branches of the ν3(A1) parallel band of 12CH3D. The simultaneous multispectrum nonlinear least-squares fitting analysis was performed in the 1140–1440 cm−1 region using 14 spectra of room temperature gas recorded with the McMath–Pierce Fourier transform spectrometer (0.005 cm−1 unapodized resolution) of the National Solar Observatory (NSO) on Kitt Peak. The measured self-broadening coefficients varied from about 0.025 cm−1 atm−1 at 296 K for high J, K transitions to about 0.09 cm−1 atm−1 at 296 K for low J, K transitions. In the case of nitrogen broadening these values ranged from about 0.023 to 0.073 cm−1 atm−1 at 296 K. The majority (>90%) of the self-pressure induced shift coefficients as well as nitrogen-pressure-induced shift coefficients was negative with values varying between approximately 0 and −0.012 cm−1 atm−1. However, similar to air-induced pressure-shift coefficients determined in an earlier study, the measured self- and nitrogen-induced pressure-shift coefficients were positive for the QR-branch transitions with J″=K″, varying from 0 to about +0.009 cm−1 atm−1. Weak line mixing effects were observed in several high-J lines with K″=3 splitting and approximate values for the off-diagonal relaxation matrix-element coefficients were determined for a few A1A2 (A+A−) split components. Comparisons are made between the measured self- and nitrogen-broadening and shift coefficients, and the results are also compared with measurements in other bands. [Copyright &y& Elsevier]

Room temperature values for self-broadened and hydrogen-broadened Lorentz halfwidth coefficients, and self and hydrogen pressure-induced shift coefficients have been measured for transitions with rotational quantum number m ranging between -24 and 24 in the 2 ← 0 band of 12C16O. The spectra were recorded with the McMath–Pierce Fourier transform spectrometer located at the National Solar Observatory on Kitt Peak. The analysis was performed using a multispectrum nonlinear least squares technique. We have compared our results with similar measurements published recently. [Copyright &y& Elsevier]

A new cryogenic Herriott cell and associated transfer optics have been designed and fabricated at Connecticut College under contract with NASA Langley Research Center to operate for the first time with the broad-band Bruker IFS-125HR Fourier transform spectrometer at the Jet Propulsion Laboratory (JPL). This 0.375 m base-length optical cavity produces an absorption path length, at 293 K, of 20.941 (±0.006) m. The Herriott cell, constructed from oxygen-free high conductivity copper, is placed inside its own vacuum enclosure, which is isolated from the transfer optics chamber by one CaF 2 window and separately evacuated. The transfer optics chamber is in turn coupled to the sample compartment of the Bruker IFS-125HR holding another set of transfer optics. The entire spectrometer, including the transfer optics chamber can be evacuated to ∼10 mTorr; the cell vacuum enclosure is cryogenically evacuated to pressures below 10 −6 Torr. A closed-cycle helium refrigerator cools the Herriott cell. Initially tested at Connecticut College for temperatures between 250 and 50 K, the system has successfully been in operation for over two years at JPL. The cell has been used for recording spectra between 75 and 250 K, achieving excellent temperature uniformity (± 0.15 K) and long term stability (< 0.05 K/day). Configured with a single indium-sealed CaF 2 window, it has provided Doppler-limited infrared absorption spectra of a number of molecular species above 2000 cm −1 to investigate detailed spectroscopic properties (e.g. molecular line parameters at temperatures and pressures relevant to planetary atmospheres). The design, performance and detailed characterization of the Herriott cell system are discussed. [ABSTRACT FROM AUTHOR]

Highlights: [•] The PH3 Pentad near 4.5μm is reanalyzed using high resolution FTIR data. [•] Over 4400 line positions and intensities are retrieved from 1950 to 2450cm−1. [•] Positions and intensities are modeled to 0.00133cm−1 and 7.7%, respectively. [•] Splitting in 53 A+A− pairs is observed for K =3,6,9 levels. [•] Nineteen measured self-broadening coefficients of and are compared. [Copyright &y& Elsevier]

Abstract: In this paper, we report measured Lorentz self-broadening and self-induced pressure-shift coefficients of 12CH3D in the ν 2 fundamental band (ν 0 ≈2200cm−1). The multispectrum fitting technique allowed us to analyze simultaneously seven self-broadened absorption spectra. All spectra were recorded at the McMath-Pierce Fourier transform spectrometer of the National Solar Observatory (NSO) on Kitt Peak, AZ with an unapodized resolution of 0.0056cm−1. Low-pressure (0.98–2.95Torr) as well as high-pressure (17.5–303Torr) spectra of 12C-enriched CH3D were recorded at room temperature to determine the pressure-broadening coefficients of 408 ν 2 transitions with quantum numbers as high as J″=21 and K =18, where K″= K′≡ K (for a parallel band). The measured self-broadening coefficients range from 0.0349 to 0.0896cm−1 atm−1 at 296K. All the measured pressure-shifts are negative. The reported pressure-induced self-shift coefficients vary from about −0.004 to −0.008cm−1 atm−1. We have examined the dependence of the measured broadening and shift parameters on the J″, and K quantum numbers and also developed empirical expressions to describe the broadening coefficients in terms of m (m =−J″, J″, and J″+1 in the Q P-, Q Q-, and Q R-branch, respectively) and K. On average, the empirical expressions reproduce the measured broadening coefficients to within 3.6%. A semiclassical theory based upon the Robert–Bonamy formalism of interacting linear molecules has been used to calculate these self-broadening and self-induced pressure-shift coefficients. In addition to the electrostatic interactions involving the octopole and hexadecapole moments of CH3D, the intermolecular potential includes also an atom–atom Lennard–Jones model. For low K (K ⩽3) with |m|⩽8 the theoretical results of the broadening coefficients are in overall good agreement (3.0%) with the experimental data. For transitions with K approaching |m|, they are generally significantly underestimated (8.8%). The theoretical self-induced pressure shifts, whose vibrational contribution is derived from results in the Q Q-branch, are generally smaller in magnitude than the experimental data in the Q P-, and Q R-branches (15.2%). [Copyright &y& Elsevier]

Air- and N2-broadening, air- and N2-pressure-induced shift coefficients and the temperature dependence exponent of the broadening coefficients and the temperature dependent coefficient of pressure-induced shifts have been determined for transitions of the ν1 band of H12C14N from 39 laboratory absorption spectra recorded at 0.005 and 0.008 cm−1 resolutions with two different Fourier transform spectrometers. The parameters were retrieved from the multispectrum nonlinear least-squares fits to the 3200–3400 cm−1 region of spectra recorded at temperatures between +26°C and −60°C. Pure samples of HCN in a 19.95 cell and a 0.958 cm cell at room temperature as well as lean mixtures of HCN in N2 or dry air in a coolable cell with a 50 cm absorption path were used in the experiments. Line parameters for N2 broadening were determined by fitting 27 spectra simultaneously while air-broadening parameters were quantified from simultaneous fits to 22 spectra. The average ratio and the standard deviation of the room-temperature air- to N2-broadening coefficient of lines with assignments between P(29) and R(28) are 0.904±0.001. Pressure-induced shift coefficients at 296 K are all negative with values between 0 and ∼−0.006 cm−1 atm−1 and different rotational dependences in the P- and R-branches. Differences between our results, previous measurements and the parameters that are reported in the 2000 edition of HITRAN (HIgh-resolution TRANsmission) database are quantified and discussed. [Copyright &y& Elsevier]