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Pressure-broadened line shapes in the 30013←00001 (ν1+4 ν 2 0 +ν3) band of 12C16O2 at 6228 cm−1 are reanalyzed using new spectra recorded with sample temperatures down to 170 K. High resolution, high signal-to-noise (S/N) laboratory measurements of line shapes (Lorentz air- and self-broadened half-width coefficients, pressure-shift coefficients and off-diagonal relaxation matrix element coefficients) as a function of gas sample temperatures for various pressures and volume mixing ratios are presented. The spectra were recorded using two different Fourier transform spectrometers (FTS): (1) the McMath-Pierce FTS located at the National Solar Observatory on Kitt Peak, Arizona (and reported in Devi et al., J Mol Spectrosc 2007;245:52-80) and, (2) the Bruker IFS-125HR FTS at the Jet Propulsion Laboratory in Pasadena, California. The 19 spectra taken at Kitt Peak were all recorded near room temperature while the 27 Bruker spectra were acquired both at room temperature and colder temperatures (170-296 K). Various spectral resolutions (0.004–0.011 cm−1), absorption path lengths (2.46–121 m) and CO2 samples (natural and 12C-enriched) were included in the dataset. To maximize the accuracies of the various retrieved line parameters, a multispectrum nonlinear least squares spectrum fitting software program was used to adjust the ro-vibrational constants (G,B,D etc.) and intensity parameters (including Herman-Wallis terms) instead of directly measuring the individual line positions and intensities. To minimize systematic residuals, line mixing (via off-diagonal relaxation matrix elements) and quadratic speed dependence parameters were included in the analysis. Contributions from other weakly absorbing bands: the 30013←00001 and 30012←00001 bands of 13C16O2, the 30013←00001 band of 12C16O18O, hot bands 31113←01101 and 32212←02201 of 12C16O2, as well as the 40013←10001 and the 40014←10002 bands of 12C16O2, present within the fitted interval were also measured. Results from previous works and new calculations are compared to present measurements, where appropriate.

In this paper we report line shape parameters of 12 CH 4 for several hundred 2ν 3 transitions in the spectral regions 5891–5996 cm −1 (P branch) and 6015–6115 cm −1 (R branch). Air- and self-broadening coefficients were measured as a function of temperature; line mixing via off-diagonal relaxation matrix element coefficients was also obtained for 47 transition pairs. In total, nearly 1517 positions and intensities were retrieved, but many transitions were too weak for the line shape study. For this analysis, we used 25 high-resolution (0.0056 and 0.0067 cm −1 ) and high signal-to-noise (S/N) spectra of high-purity 12 CH 4 and the same high-purity 12 CH 4 broadened by dry air recorded at different sample temperatures between 130 K and 295 K with the Bruker IFS 125HR Fourier transform spectrometer at JPL. Three different absorption cells were used (1) a White cell set to a path length of 13.09 m for room temperature data, (2) a single-pass 0.2038 m long coolable cell (for self-broadening) and (3) a multipass cell with 20.941 m total path coolable Herriott cell (for air-broadening). In total there were 13 spectra with pure 12 CH 4 (0.27–599 Torr) and 12 air-broadened spectra with total sample pressures of 80–805 Torr and volume mixing ratios (VMR) of methane between 0.18 and 1.0. An interactive multispectrum nonlinear least-squares technique was employed to fit the individual P10–P1 and R0–R10 manifolds in all the spectra simultaneously. Results obtained from the present analysis are compared to other recent measurements.

Accurate knowledge of spectral line shape parameters is important for infrared transmission and radiance calculations in the terrestrial atmosphere. In this paper, we report the self- and air-broadened Lorentz half-widths, pressure-induced shifts and line mixing coefficients (via off-diagonal relaxation matrix elements) along with their temperature dependences for methane ν2+ν3 absorption lines in the 4500–4630 cm−1 region of the Octad. For this, we recorded 14 high-resolution, high signal to noise ratio (S/N) spectra of high-purity (99.95% 12C-enriched) samples of pure methane and its dilute mixtures in dry air between 298 K and 148 K. A Bruker IFS 125HR Fourier transform spectrometer (FTS) at the Jet Propulsion Laboratory, Pasadena, California, was used to obtain the experimental data. The absorption cell used for this study was a specially built 20.38 cm long coolable cell installed in its sample compartment. The sample pressures for the pure 12CH4 spectra were 4.5−385 Torr; for the air-broadened spectra the total pressures ranged between 95 and 300 Torr with the methane volume mixing ratios between 0.04 and 0.097. All 14 spectra were fitted simultaneously using an interactive multispectrum nonlinear least-squares curve fitting technique. The results are compared to values reported in the literature.

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 CaF2 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 (

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. © 2014 Elsevier Inc. All rights reserved.

Retrievals of atmospheric composition from near-infrared measurements require measurements of airmass to better than the desired precision of the composition. The oxygen bands are obvious choices to quantify airmass since the mixing ratio of oxygen is fixed over the full range of atmospheric conditions. The OCO-2 mission is currently retrieving carbon dioxide concentration using the oxygen A-band for airmass normalization. The 0.25% accuracy desired for the carbon dioxide concentration has pushed the required state-of-the-art for oxygen spectroscopy. To measure O2 A-band cross-sections with such accuracy through the full range of atmospheric pressure requires a sophisticated line-shape model (Rautian or Speed-Dependent Voigt) with line mixing (LM) and collision induced absorption (CIA). Models of each of these phenomena exist, however, this work presents an integrated self-consistent model developed to ensure the best accuracy. It is also important to consider multiple sources of spectroscopic data for such a study in order to improve the dynamic range of the model and to minimize effects of instrumentation and associated systematic errors. The techniques of Fourier Transform Spectroscopy (FTS) and Cavity Ring-Down Spectroscopy (CRDS) allow complimentary information for such an analysis. We utilize multispectrum fitting software to generate a comprehensive new database with improved accuracy based on these datasets. The extensive information will be made available as a multi-dimensional cross-section (ABSCO) table and the parameterization will be offered for inclusion in the HITRANonline database.

Accurate individual line intensities have been measured for the five interacting bands ν 10 , ν 8 , ν 7 , ν 4 and ν 6 of ethylene-1- 13 C using a multispectrum nonlinear least squares fitting technique. The measured intensities have been very satisfactorily fit leading to the determination of precise vibrational transition moments. A calculated spectrum accounting for the various rovibrational interactions has been generated. Such a spectrum should be useful for the planetary atmosphere modeling-community. Lorentz self-broadened half-width coefficients have also been measured for nearly 300 transitions in the strongest ν 7 band.

Line positions, Lorentz air-broadened half width and air pressure-induced shift coefficients have been measured for nearly 200 transitions in the ν 4 band of 13 CH 4 from high-resolution spectra recorded with the McMath-Pierce Fourier transform spectrometer. Three room temperature spectra of 13 CH 4 used in the previous study of Malathy Devi et al. (Air-broadened Lorentz halfwidths and pressure-induced line shifts in the ν 4 band of 13 CH 4 . Appl. Opt. 1988; 27: 2296–2308) were analyzed together with a large number of additional spectra of self- and air-broadened CH 4 recorded at 210–314 K and one room-temperature spectrum of self-broadened 13 CH 4 . Analyses applying the multispectrum nonlinear least squares fitting technique were performed to retrieve the spectral line parameters. In addition to air-broadened half width and shift coefficients, self-broadened half width and shift coefficients were determined for at least 56 13 CH 4 ν 4 transitions. Off-diagonal relaxation matrix element coefficients for air-broadened line mixing were also determined for 28 pairs of P and R transitions in a number of J manifolds, and mixing parameters for self-broadening were also determined for some of these pairs. Temperature-dependences of the pressure-induced shift and mixing parameters for the 13 CH 4 lines could not be determined from the spectra used in the present analysis, but temperature dependences of the half width coefficients were determined for the strongest transitions. The results of this study are compared with other studies of air- and self-broadened 13 CH 4 and 12 CH 4 .

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 CO 2 spectra broadened by O 2 . These spectra were analyzed to measure O 2 -broadened half-width coefficients, O 2 -induced pressure-shift coefficients and speed dependent parameters for transitions in the 30013←00001 and 30012←00001 bands of 16 O 12 C 16 O located near 6227 and 6348 cm −1 , respectively. All spectra were obtained at room temperature using the long path, 6 m 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 6120–6280 cm −1 (30013←00001) and 6280–6395 cm −1 (30012←00001) spectral regions. 16 of the 19 spectra analyzed in this work were self broadened and three spectra were lean mixtures of CO 2 in O 2 . The volume mixing ratios of CO 2 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 N 2 -broadened half-width and pressure-shift coefficients were computed from measured air- and O 2 -broadened width and shift coefficients.

Line positions, intensities, Lorentz self- and N2-broadened half-width coefficients have been measured for PQ3, PQ2, PQ1, RQ0, RQ1, RQ2, and RQ3 sub-band transitions in the ν9 fundamental band of 12C2H6. A multispectrum nonlinear least-squares fitting technique was used to fit up to 17 high-resolution (∼0.00156 cm−1), room temperature absorption spectra of pure (99.99% chemical purity) natural sample of ethane and lean mixtures of the high-purity ethane diluted with N2. A Bruker IFS 120HR Fourier transform spectrometer located at the Pacific Northwest National Laboratory (PNNL), in Richland, Washington was used to record the data. A standard Voigt line shape was assumed to fit all the data since no line mixing or other non Voigt line shapes were required to fit any of the spectra used in the analysis. Short spectral intervals (∼2–2.5 cm−1) of all 17 spectra covering a specific PQ or RQ sub-band were fit simultaneously. For the first time in an ethane band, pressure-broadened half-width coefficients were determined for the torsional-split components. However, for better reliability of the retrieved coefficients for the weaker components (transitions with large intensity ratios of 4:1 or 3:1 for most K levels between the strong and weak components), constraints were used such that the half-width coefficients of both torsional-split components for a given J were identical for a specific broadening gas. No pressure-induced shift coefficients were necessary to fit the spectra to their noise level. The present study revealed for the first time the dependence of self- and N2-broadened half-width coefficients upon the J, K quantum numbers of the transitions in ethane. A number of transitions belonging to the ν9+ν4−ν4 and the ν9+2ν4−2ν4 hot bands were also observed in the fitted regions and measurements were made when possible.

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 314 K using the National Solar Observatory's 1 m Fourier transform spectrometer at the McMath-Pierce solar telescope. The complete data set included 60 high-resolution (0.006–0.01 cm−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 5–15 cm−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.

Lorentz air-broadened half widths, pressure-induced shifts and their temperature dependences have been measured for over 430 transitions (allowed and forbidden) in the v4 band of (CH4)-12 over the temperature range 210 to 314 K. A multispectrum non linear least squares fitting technique was used to simultaneously fit a large number of high-resolution (0.006 to 0.01/cm) 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 v4 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.

Line positions and strengths of 16O13C16O (636), 16O13C18O (638) and 16O13C17O (637), and 18O13C18O (838) bands were measured using natural and 13C- and 18O-enriched samples of CO2 at room temperature. Twenty-five near infrared (NIR) absorption spectra were recorded at 0.01–0.013 cm−1 resolution with the McMath–Pierce Fourier transform spectrometer located at the National Solar Observatory on Kitt Peak, Arizona. Absorption cells with optical path lengths ranging from 0.347 m to 385 m were used with pressures ranging between 0.5 and 147 torr. Line strengths were obtained for 17 bands of (636) between 4697 and 6797 cm−1, 13 bands of (638) between 2192 and 4954 cm−1, 4 bands of (637) between 3437 and 4981 cm−1 and 7 bands of (838) between 2182 and 4888 cm−1. Band strengths and Herman–Wallis-like F-factor coefficients were determined from least-squares fits to over 2000 measured transition intensities involving 41 different bands. The observed line positions of several bands were analyzed to obtain the upper state term values and rotational constants. Five of the 18O13C18O bands and two of the 16O13C18O bands were modeled for the first time.

This study provides the first direct experimental measurements of the off-diagonal relaxation matrix element coefficients for line mixing in air-broadened methane spectra for any vibrational band and the first off diagonal relaxation matrix elements associated with line mixing for pure methane in the ν 2 + ν 3 band of 12 CH 4 . The speed-dependent Voigt profile with line mixing is used with a multispectrum nonlinear least squares curve fitting technique to retrieve the various line parameters from 11 self-broadened and 10 air-broadened spectra simultaneously. The room temperature spectra analyzed in this work are recorded at 0.011 cm −1 resolution with the McMath-Pierce Fourier transform spectrometer located at the National Solar Observatory, Kitt Peak, Arizona. The off-diagonal relaxation matrix element coefficients of ν 2 + ν 3 transitions between 4410 and 4629 cm −1 are reported for eighteen pairs with upper state J values between 2 and 11. The observed line mixing coefficients for self broadening vary from 0.0019 to 0.0390 cm −1 atm −1 at 296 K. The measured line mixing coefficients for air broadening vary from 0.0005 to 0.0205 cm −1 atm −1 at 296 K.

Line position, intensity and line shape parameters (Lorentz widths, pressure shifts, line mixing, speed dependence) are reported for transitions of the 30013 ← 00001 band of 16O12C16O (ν0 = 6227.9 cm−1). The results are determined from 26 high-resolution, high signal-to-noise ratio spectra recorded at room temperature with the McMath-Pierce Fourier transform spectrometer. To minimize the systematic errors of the retrieved parameters, we constrained the multispectrum nonlinear least squares retrieval technique to use quantum mechanical expressions for the rovibrational energies and intensities rather than retrieving the individual positions and intensities line by line. Self- and air-broadened Lorentz width and pressure-induced shift, speed dependence and line mixing (off-diagonal relaxation matrix elements) coefficients were adjusted individually. Errors were further reduced by simultaneously fitting the interfering absorptions from the weak 30012 ← 00001 band of 16O13C16O as well as the weak hot bands 31113 ← 01101, 32213 ← 02201, 40014 ← 10002 and 40013 ← 10001 of 16O12C16O in this spectral window. This study complements our previous work on line mixing and speed dependence in the 30012 ← 00001 band (ν0 = 6347.8 cm−1) [V.M. Devi, D.C. Benner, L.R. Brown, C.E. Miller, R.A. Toth, J. Mol. Spectrosc. 242 (2007) 90-117] and provides key data needed to improve atmospheric remote sensing of CO2.

Line positions and strengths of 16O12C18O (628), 18O12C18O (828) and 17O12C18O (728) were measured between 2200 and 7000 cm−1 using 22 near infrared (NIR) absorption spectra recorded at 0.01–0.013 cm−1 resolution with the McMath–Pierce Fourier transform spectrometer located at the National Solar Observatory on Kitt Peak, Arizona. These data were obtained at room temperature using absorption cells with optical path lengths ranging from 2.4 to 385 m; the cells were filled with natural and 18O-enriched samples of CO2 at pressures ranging from 0.54 to 252 torr. The observed line positions were analyzed to obtain the upper state band centers and rotational constants for 17 bands of 16O12C18O, 19 bands of 18O12C18O and 8 bands of 17O12C18O. The majority of the 18O12C18O and 17O12C18O bands were measured for the first time. In addition, the rotational constants for the lower states 00001, 01101e and 01101f were derived for all three species using the method of combination differences in which the averaged values obtained from the line positions of two or more bands were least-squares-fitted. Rovibrational parameters were also obtained for the 02201e, 02201f, 10002 and 10001 states of 18O12C18O. The line position analysis revealed that transitions of the levels 38 ⩽ J′ ⩽ 46 of the 11111f ← 01101f band of 18O12C18O are perturbed. Perturbed transitions were also observed for the 12212 ← 02201 band and in the high-J transitions (J′ ⩾ 49) of the 20012 ← 00001 band of 18O12C18O. Band strengths and Herman–Wallis-like F-factor coefficients were determined for 21 bands of 16O12C18O, 25 bands of 18O12C18O and 8 bands of 17O12C18O from least-squares fits to more than 3700 measured transition intensities; band strengths and line positions for 34 of these bands were obtained for the first time.

Intensity and line shape parameters which predict spectral lines with absolute accuracies better than 0.3% have been determined for transitions of the 30012 ← 00001 band of 16 O 12 C 16 O centered near 6348 cm −1 from 26 high resolution, high signal-to-noise ratio spectra recorded at room temperature with the McMath–Pierce Fourier transform spectrometer. To maximize the accuracies of the retrieved parameters, the multispectrum non-linear least squares retrieval technique was modified to adjust the rovibrational constants ( G , B , D , etc.) and intensity parameters, including Herman–Wallis terms, rather than retrieving the individual positions and intensities. Speed-dependent Voigt line shapes with line mixing were required to remove systematic errors in the fit residuals. Self- and air-broadening (widths and pressure-induced shifts, speed dependence parameters) and line mixing (off-diagonal relaxation matrix elements) coefficients were thus obtained in the multispectrum fit. Remaining errors were minimized by fitting the weak 30011 ← 00001 band of 16 O 13 C 16 O as well as the weak hot bands 31112 ← 01101, 32212 ← 02201, 40012 ← 10001, and 40013 ← 10002 of 16 O 12 C 16 O that contribute interfering absorptions in this spectral window. This study presents the most extensive set of measurements to date for self- and air-broadening and self- and air-shift coefficients of a near infrared band of CO 2 . This is also the first study where line mixing parameters have been experimentally determined for any parallel CO 2 band.

Line positions and strengths of 12 C 16 O 2 were measured between 4550 and 7000 cm −1 using near infrared absorption spectra recorded at 0.01–0.013 cm −1 resolution with the McMath-Pierce Fourier transform spectrometer located at the National Solar Observatory at Kitt Peak, Arizona. These were retrieved from 42 laboratory spectra obtained at room temperature with five absorption cells having various optical path lengths (from 0.1 to 409 m) filled with natural and enriched samples of CO 2 at pressures ranging from 2 to 581 Torr. In all, band strengths and Herman–Wallis-like F -factor coefficients were determined for 58 vibration–rotation bands from the least-squares fits of over 2100 unblended line strengths; strengths of 34 of these bands had not been previously reported. Band strengths in natural abundance generally ranged from 3.30 × 10 −20 to 2.8 × 10 −25 cm −1 /molecule cm −2 at 296 K. It was found that the high J transitions ( J ′ ⩾ 61) of the 20012 ← 00001 band centered at 4977.8347 cm −1 are perturbed, affecting both measured positions and strengths. Two other interacting bands, 21113e ← 01101e and 40002e ← 01101e, were also analyzed using degenerate perturbation theory. Comparisons with corresponding values from the literature indicate that absolute accuracies better than 1% and precisions of 0.5% were achieved for the strongest bands.

In this paper, we report measured Lorentz self-broadening and self-induced pressure-shift coefficients of 12CH3D in the ν2 fundamental band (ν0 ≈ 2200 cm−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 0.0056 cm−1. Low-pressure (0.98–2.95 Torr) as well as high-pressure (17.5–303 Torr) spectra of 12C-enriched CH3D were recorded at room temperature to determine the pressure-broadening coefficients of 408 ν2 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 0.0896 cm−1 atm−1 at 296 K. All the measured pressure-shifts are negative. The reported pressure-induced self-shift coefficients vary from about −0.004 to −0.008 cm−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 QP-, QQ-, and QR-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 QQ-branch, are generally smaller in magnitude than the experimental data in the QP-, and QR-branches (15.2%).

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 m2 band of H 12 C 14 N centered near 712 cm � 1 . Infrared spectra of HCN in the 14-lm region were obtained at high resolution (0.002–0.008 cm � 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 1.2 cm � 1 atm � 1 at 296 K, and the air-broadening coefficients range from 0.08 to 0.14 cm � 1 atm � 1 at 296 K. 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 selfbroadening 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.

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 12 C 16 O. 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.

We have analyzed the methyl fluoride R Q(J,0) Q branch lines located near 1475 cm −1 using a simultaneous multi-spectrum fitting technique. In this analysis we have used previously recorded diode-laser data in which we collected many data points covering only one or two Q branch lines in a particular run. The analysis consists of simultaneously fitting 57 spectra collected with numerous pressure and path length conditions for all absorption lines. The data are concatenated to create one continuous spectrum of the Q branch. We have determined the intensity and self-broadened widths at 296 K for 23 R Q ( J ,0) lines.

Line intensities of the two 12 C 16 O 2 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.

Extensive high-resolution experimental determination is provided for air- and N2-broadening and pressure shift coefficients for the two 13 C 16 O 2 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 12 C 16 O 2 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 12 CO 2 and 13 CO 2 in the same fit we were able to obtain a consistent set of line parameters for both molecules. The results obtained for the 12 CO 2 and 13 CO 2 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.

Self- and hydrogen-broadening coefficients and pressure-shift coefficients for the first overtone band transitions of 12 C 16 O 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) 12 C 16 O 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 12 C 16 O at room temperature.

Absolute intensities of 376 16O3 lines in the 9–11 μm region have been determined from high-resolution infrared absorption spectra recorded at room temperature using a Fourier transform spectrometer. The ozone samples were contained in a glass cell having crossed IR-transmitting and UV-transmitting paths, and the UV absorption at 254 nm was used to monitor ozone concentrations in the cell. A multispectrum nonlinear least squares fitting procedure was used to determine intensities for 366 lines in the ν3 fundamental band and 10 lines in the ν1 band. The absolute accuracy of these intensity values ranges from 2% for the strongest, most well determined lines to 4 or 5% for the weakest lines measured. On average, our measured intensities are approximately 1% larger than the values on current spectroscopic databases.

A multispectrum nonlinear least-squares fitting technique has been used to determine the absolute intensities for approximately 1500 spectral lines in 36 vibration - rotation bands Of C-12O2-16 between 3090 and 3850/ cm. A total of six absorption spectra of a high- purity (99.995% minimum) natural sample of carbon dioxide were used in the analysis. The spectral data (0.01/cm resolution) were recorded at room temperature and low pressure (1 to 10 Torr) using the McMath-Pierce Fourier transform spectrometer of the National Solar Observatory (NSO) on Kitt Peak. The absorption path lengths for these spectra varied between 24.86 and 385.76 m. The first experimental determination of the intensity of the theoretically predicted 2(nu)(sub 2, sup 2) + nu(sub 3) "forbidden" band has been made. The measured line intensities obtained for each band have been analyzed to determine the vibrational band intensity, S(sub nu), in /cm/( molecule/sq cm) at 296 K, square of the rotationless transition dipole moment |R|(exp 2) in Debye, as well as the nonrigid rotor coefficients. The results are compared to the values listed in the 1996 HITRAN database which are obtained using the direct numerical diagonalization (DND) technique as well as to other published values where available.

High quality and precise measurements of self-broadened and self-shift coefficients in the fundamental band of 12C16O were made using spectra recorded at room temperature with the high-resolution (0.0027 cm-1) McMath-Pierce Fourier transform spectrometer located at the National Solar Observatory on Kitt Peak, Arizona. The spectral region under investigation (2008–2247 cm-1) contains the P(31) to R(31) transitions. The data were obtained using a high-purity natural isotopic sample of carbon monoxide and two absorption cells with pathlengths of 4.08 and 9.98 cm, respectively. Various pressures of CO were used, ranging between 0.25 and 201.2 Torr. The results were obtained by analyzing five spectra simultaneously using a multispectrum nonlinear least-squares fitting technique. The self-broadened coefficients ranged from 0.0426(2) cm-1 atm-1 at 296 K to 0.0924(2) cm-1 atm-1 at 296 K, while the pressure-induced shift coefficients varied between −0.0042(3) cm-1 atm-1 at 296 K and +0.0005(1) cm-1 atm-1 at 296 K. The value in parentheses is the estimated uncertainty in units of the last digit. The self-broadened coefficients of lines with same values of m in the P and R branches agree close to within experimental uncertainties while the self-shift coefficients showed considerable variation within and between the two branches. The mean value of the ratios of P branch to R branch self-broadened coefficients was found to be 1.01 with a standard deviation of ±0.01. Comparisons of the results with other published data were made.

In this paper we report the pressure broadening and the pressure-induced line shift coefficients for 46 individual rovibrational lines in both the (12)C(16)O2, 00(sup 0)1-(10(sup 0)0-02(sup 0)0)I, and 00(sup 0)1-(10(sup 0)0-02(sup 0)0)II, laser bands (laser band I centered at 960.959/cm and laser band II centered at 1063.735/cm) determined from spectra recorded with the McMath-Pierce Fourier transform spectrometer. The results were obtained from analysis of 10 long-path laboratory absorption spectra recorded at room temperature using a multispectrum nonlinear least-squares technique. Pressure effects caused by both air and nitrogen have been investigated. The air-broadening coefficients determined in this study agree well with the values in the 1996 HITRAN database; ratios and standard deviations of the ratios of the present air-broadening measurements to the 1996 HITRAN values for the two laser bands are: 1.005(15) for laser band I and 1.005(14) for laser band II. Broadening by nitrogen is 3 to 4% larger than that of air. The pressure-induced line shift coefficients are found to be transition dependent and different for the P- and R-branch lines with same J" value. No noticeable differences in the shift coefficients caused by air and nitrogen were found. The results obtained are compared with available values previously reported in the literature.

Data from the Halogen Occultation Experiment (HALOE) provide the first opportunity to examine solar center-to-limb relative intensity measured exoatmospherically at wavelengths from 2.4 to 10 μm. The data were obtained from limb-to-limb scans across the solar equator on days of very low activity in May 1994. Coefficients for a function describing limb darkening are obtained at eight infrared wavelengths using a nonlinear least-squares fitting technique. Relative intensities produced by the limb-darkening functions are precise to 0.1% (2σ). From the limb-darkening coefficients, it is possible to calculate temperature information about the photosphere. At each of the eight HALOE wavelengths, the brightness temperature from the flux, T b disk(λ), and the temperature as a function of monochromatic optical depth, T(τλ), are determined and normalized using Kondratyev et al. (1965) and calibrated Pierce (1954) central intensity measurements. The two temperature quantities are compared with the predictions of Vernazza, Avrett, and Loeser's (1976) model M, and in general there is good agreement. The largest differences occur between 2.4 and 3 μm and suggest that the central intensities used in this spectral region are low.

High-resolution (0.01/cm) absorption spectra of lean mixtures of CH4 in dry air were recorded with the McMath-Pierce Fourier transform spectrometer (FTS) of the National Solar Observatory on Kitt Peak at various temperatures between 24 and -61 C. The spectra have been analyzed to determine the values at room temperature of pressure-broadened widths and pressure-induced shifts of more than 740 transitions. The temperature dependence of air-broadened widths and pressure-induced shifts was deduced for approx. 370 transitions in the nu(sub 1) + nu(sub 4), nu(sub 3) + nu(sub 4), and nu(sub 2) + nu(sub 3) bands of (12)CH4 located between 4118 and 4615/cm. These results were obtained by analyzing a total of 29 spectra simultaneously using a multi-spectral non-linear least-squares fitting technique. This new technique allowed the determination of correlated spectral line parameters (e.g. intensity and broadening coefficient) better than the procedure of averaging values obtained by fitting the spectra individually. This method also provided a direct determination of the uncertainties in the retrieved parameters due to random errors. For each band analysed in this study the dependence of the various spectral line parameters upon the tetrahedral symmetry species and the rotational quantum numbers of the transitions is also presented.

Lorentz-broadening coefficients and pressure-induced line-shift coefficients of 34 individual lines have been determined for the P(40) to R(40) vibration-rotation transitions in the nu(3) fundamental of CO2 using N2 as the buffer gas. The parameters were derived from 0.01/cm resolution infrared absorption spectra recorded using the McMath Fourier transform spectrometer and a nonlinear, least-squares fitting algorithm. It is concluded that the N2-broadening coefficients obtained in the present study agree well with recent high resolution measurements. The results are considered to be of importance not only for predicting the infrared spectrum of the atmosphere due to CO2 absorption or emission but also for verifying theoretical calculations.

Lorentz nitrogen-broadening coefficients and nitrogen pressure-induced shift coefficients have been measured for six lines in the ν 1 band and 98 lines in the ν 3 band of H 2 16 O. The results were obtained from analysis of 10 high-resolution (0.01 cm −1 ) infrared absorption spectra recorded at room temperature using the McMath Fourier transform spectrometer of the National Solar Observatory on Kitt Peak. The analysis was performed using a nonlinear least-squares spectrum fitting procedure. The measured nitrogen-broadening coefficients ranged from ∼0.04 to ∼0.104 cm −1 atm −1 , while the nitrogen pressure-induced shift coefficients varied between ∼+0.004 and ∼−0.011 cm −1 atm −1 . The majority of the measured pressure-induced shift coefficients (>90%) were found to be negative. The results are compared with previous values reported in the literature, where available.

Lorentz-broadening and pressure-induced line-shift coefficients are determined experimentally for 126 transitions in the nu2 band of D2(O-16) from laboratory spectra with a Fourier-transform spectrometer. A nonlinear least-squares fitting procedure is employed to measure transitions up to J double-prime = 12 in the buffer gases air, nitrogen, and oxygen. The N2-broadening/O2-broadening coefficient ratio is correlated with the magnitude of the O2-broadening coefficient, and the pressure coefficients are not correlated with line widths.

Molecular band models are used to derive absorption and pressure coefficients for the methane absorption spectrum from 4500 to 10500 A at intervals of 10 A. These coefficients provide a necessary basis for the interpretation of the large methane absorptions in the atmospheres of the major planets. Although only coefficients for the “random” or “Goody” band model are derived, the equivalence between these and the “regular” of “Elasser” coefficients is demonstrated. The effects of pressure on the absorption are surprisingly small, leading to large values of the pressure coefficient quite unlike any previous application of the band-model theory. They indicate a pseudo-continuum character of the methane spectrum throughout the visible and near infrared. A spectrum synthesis calculation using the derived coefficients shows the close fit to experimental data that can be realized.

Laboratory band-model absorption coefficients of CH4 were used to calculate the Uranus spectrum from 5400 to 10,400 A. A good fit for both strong and weak bands for the Uranus spectrum over the entire wavelength interval was achieved; three atmospheric models were employed: (1) a reflecting layer model; (2) a homogeneous scattering layer model; and (3) a clear atmosphere sandwiched between two scattering layers. The spectrum for the reflecting layer model shows serious discrepancies but indicates that large amounts of CH4 are necessary to reproduce the Uranus spectrum. Both scattering models gave reasonably good fits; the homogeneous model requires a particle scattering albedo of at least 0.998 and an abundance per scattering mean free path of about 1 km-am. For the sandwich model, a continuum single scattering albedo of 0.995 was derived for the upper scattering layer, and the scattering optical depth variable wavelength was consistent with Rayleigh scattering.

Absolute line intensities have been determined at room temperature for a total of 22 transitions belonging to rP and pP subbands in the ν6(E) perpendicular band of 12CH3D between 1062 and 1114 cm−1 under Doppler-limited resolution using a tunable diode-laser spectrometer system. Although the line intensities were determined with good precision (≈3%), the squared vibrational transition dipole matrix element derived from each line intensity showed large variations (≈500%) indicating intensity perturbations, possibly caused by Coriolis interactions between the ν3, ν5, and ν6 fundamentals. The “Herman-Wallis” F-factor coefficients derived from the rP and pP subband transitions were significantly different from each other, but compared well with those reported in a recent study by M. Delaveau (Ph.D. thesis, Universite de Paris-Sud, Orsay, 1985) using a Fourier transform spectrometer. Room temperature air- and nitrogen-broadened halfwidths have also been determined for 24 lines. The average of the ratios of nitrogen- to air-broadened halfwidths was 1.01 with a standard deviation of 0.01, giving almost equal broadening efficiencies for nitrogen and air. Room temperature self-broadened halfwidths were derived for two transitions with a mean value of 0.081 ± 0.001 cm−1 atm−1 at 296 K.

Absolute line intensities for several individual vibration-rotation transitions in the ν 2 bands of HDO and D 2 O have been determined at room temperature from laboratory spectra recorded with a tunable diode laser spectrometer. Two tunable semiconductor diode lasers operating in the 1250- to 1350- and 1060- to 1140-cm −1 spectral regions have been used in the recording of the data. Comparisons are made with previously published results where appropriate.

Nitrogen- and air-broadened Lorentz halfwidths have been determined for 29 lines in the P and R branches of the (ν4 + ν5)0 combination band of 12C2H2 using a tunable diode laser spectrometer. Two tunable diode lasers operating in the region 1250–1380 cm−1 were used in recording the data. For nitrogen broadening, the measured halfwidths at 296 K decrease from about 0.11 cm−1 atm−1 at |m| = 1 to about 0.05 cm−1 atm−1 at |m| = 30, where m = J″ + 1 for R-branch lines, m = −J″ for P-branch lines, and J″ is the lower state rotational quantum number. On the average, the air-broadened halfwidths are 97% of the N2-broadened halfwidths.

Absolute intensities for over 800 transitions belonging to twelve bands of (C-12)(O-16)2, (O-16)(C-12)(O-18), (O-16)(C-12)(O-17), and (O-16)(C-13)(O-18) molecules in the 2395-2680/cm spectral region have been derived using a nonlinear least-squares spectral fitting procedure. The data used in the analysis were recorded at room temperature and low pressure with the 0.01/cm resolution Fourier transform spectrometer in the McMath solar telescope complex at the National Solar Observatory. The measured intensities obtained for each band have been analyzed to derive the vibrational band intensity and F-factor coefficients. The results are compared with other published values.

Air-broadened half-widths of 18 transitions in the nu6 band of H2O2 between 1252/cm and 1291/cm have been determined from spectra recorded at room temperature using a tunable diode laser spectrometer. The preparation of the H2O2 gas samples for the measurements is described, and the data analysis is discussed, including the derivation of Lorentz broadening coefficients and the contribution of molecular collisions to the measured Lorentz half-widths. For the 18 transitions, the half-widths varied from 0.0923/cm/atm to 0.1155/cm/atm at 296 K, with a mean value of 0.1020/cm/atm. An error of less than 10 percent is estimated for these results.

Air- and nitrogen-broadened half-widths and line shifts at room temperature for more than 60 individual vibration-rotation transitions in the nu1 fundamental band of (O-16)3 and several transitions in the nu3 band were determined from infrared absorption spectra. These spectra were recorded at 0.005/cm resolution with a Fourier-transform spectrometer. A tunable-diode-laser spectrometer operating in the 1090-1150/cm region was also used to record data on oxygen-, nitrogen-, and air-broadened half-widths for selected individual transitions. The nitrogen- and air-broadened half-widths determined by these two different measurement techniques are consistent to within 4 percent. The results are in good agreement with other published measurements and calculations.

Air-broadened and N2-broadened halfwidth and pressure shift coefficients of 294 transitions in the nu4 and nu2 bands of C-12H4 have been measured from laboratory absorption spectra recorded at room temperature with the Fourier transform spectrometer in the McMath solar telescope facility of the National Solar Observatory. Total pressures of up to 551 Torr were employed with absorption paths of 5-150 cm, CH4 volume mixing ratios of 2.6 percent or less, and resolutions of 0.005 and 0.01/cm. A nonlinear least-squares spectral fitting technique has been utilized in the analysis of the twenty-five measured spectra. Lines up to J double-prime = 18 in the nu4 band and J double-prime = 15 in the nu2 band have been analyzed.

Air-broadened and N2-broadened halfwidths at room temperature for twenty-five transitions in the nu-4 fundamental band of (C-12)H4 have been determined from IR absorption spectra recorded with a tunable diode laser spectrometer. Two tunable diode lasers operating in the 1250-1380-kayser region were used to obtain these data. Air-broadened halfwidths for twenty of these lines were also determined from additional spectra recorded at 0.01-kayser resolution with the Fourier transform spectrometer in the McMath solar telescope complex on Kitt Peak. The air-broadened halfwidths obtained from these two techniques are very consistent with agreement better than 3 percent in most cases.

Air-broadened halfwidths and pressure-induced line shifts in the nu(4) fundamental of C-13H4 were determined from spectra recorded at room temperature and at 0.01/cm resolution using a Fourier transform spectrometer. Halfwidths and pressure shifts were determined for over 180 transitions belonging to J-double prime values of less than or = to 16. Comparisons of air-broadened halfwidths and pressure-induced line shifts made for identical transitions in the nu(4) bands of C-12H4 and C-13H4 have shown that C-13H4 air-broadened halfwidths are about 5 percent smaller than the corresponding C-12H4 halfwidths, and the pressure shifts for C-13H4 lines are about 5-15 percent larger than those for C-12H4.

Tunable diode laser measurements of air-broadened and N2-broadened halfwidths are reported for 23 lines in the nu(4) band of C-13H4, between 1260 and 1360/cm. For all lines, at least three scans of each of four or more pressures were recorded. The experimental halfwidths presently obtained for C-13H4 are both larger and smaller than the U.S. Air Force Geophysics Laboratory values.