The Fourier transform spectrometer of the Université Pierre et Marie Curie QualAir platform.

A Bruker Optics IFS 125HR Fourier transform spectrometer (FTS) and the Laboratoire de Physique Moléculaire pour l'Atmosphère et l'Astrophysique retrieval algorithm were adapted for ground based atmospheric measurements. As one of the major instruments of the experimental research platform QualAir, this FTS is dedicated to study the urban air composition of large megacity such as Paris. The precise concentration measurements of the most important atmospheric pollutants are a key to improve the understanding and modeling of urban air pollution processes. Located in the center of Paris, this remote sensing spectrometer enables to monitor many pollutants. Examples for NO(2) and CO are demonstrating the performances of this new experimental setup.

Development of a stabilized low temperature infrared absorption cell for use in low temperature and collisional cooling experiments.

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 80K or with liquid helium from 80K 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 10.5K and at pressures near 1 Torr have been recorded. The He-pressure broadening parameter (gamma(0) = 0.3 cm(-1) atm(-1)) has been derived from the simultaneous analysis of four spectra at different pressures.

Diode laser emission linewidth determination: application to H2O line profile studies in the 5 and 1.4 microm regions.

In order to study absorption line profiles using the stabilized diode laser spectrometer of Laboratoire de Physique Moléculaire et Applications (LPMA), a reliable determination of the emission line shape of different diodes laser is needed. In the near infrared region (1.39 and 1.66 microm) we used Distributed Feed Back diode lasers which operate around room temperature and in the middle infrared (5 and 8 microm) we used lead salt diode lasers cooled in a helium closed cycle cryostat or in a liquid nitrogen dewar. Some results obtained in H2O line profile studies in the 1.39 and 5 microm regions are presented as examples demonstrating how absorption line profile measurements can lead to erroneous values of the spectroscopic parameters when the contribution of the diode laser emission line width is neglected.

Pressure broadening study at low temperature: application to methane.

We studied the R(0) line profile in the CH4 v4 band from room temperature to 188 K with N2 as a perturber, to 100 K with O2 as perturber, and from room temperature to 15 K using He as a perturber. The N2 and O2 measurements were performed over a total pressure range of 15-110 mbar, and for the He measurements the maximum sample pressure at 15 K was 1.10 mbar. Broadening parameters were determined, taking into account the confinement narrowing (Dicke effect), and narrowing parameters, deduced from the soft or hard collision model, are compared with the dynamic friction coefficient calculated values. We also obtained preliminary values for the temperature dependence of the N2, O2 and He line broadening parameters for this transition.

High-Lying Rotational Levels of Water: An Analysis of the Energy Levels of the Five First Vibrational States.

As a continuation of the work carried out on the ground and (010) vibrational states of water (R. Lanquetin, L. H. Coudert, and C. Camy-Peyret, 1999, J. Mol. Spectrosc. 195, 54-57), rotational energy levels for these two states are revisited here and new accurate rotational energy levels are considered for the three next vibrational states, that is, the (020), (100), and (001) states. Experimental rotational energies, along with their uncertainties, are retrieved through analyses of already published data sets and of discharge and flame emission spectra. The maximum value of J for the obtained levels is 25 for the ground state, 21 for the (010) state, and 20 for the three next states. Based on the bending-rotation Hamiltonian approach (L. H. Coudert, 1997, J. Mol. Spectrosc. 181, 246-273), a new theoretical approach is proposed to calculate rotational energies in the five interacting vibrational states under consideration and is used to carry out an analysis of the experimental energies. Comparisons with other existing energy level data sets are also presented. Copyright 2001 Academic Press.

Absolute Intensities of the nu(1) and nu(3) Bands of (16)O(3).

New experimental data on the nu(1) and nu(3) bands of (16)O(3) improving the value of absolute line intensities have been obtained. The intensities of 295 lines have been measured with an average accuracy between 2.5% and 3% and the rotational expansion of the transition moment operators for the nu(1) and nu(3) bands has been deduced. Finally, a complete listing of line intensities has been computed with an intensity cutoff of 1x10(-25) cm(-1)/molecule cm(-2). Copyright 2001 Academic Press.

High-Order Resonances in the Water Molecule.

The water-vapor spectra in the near-infrared and visible region were reanalyzed with the purpose of finding experimental evidences of unusual high-order resonance between "dark" high-bending and "bright" stretch vibration states. About 70 transitions to the (050), (060), (070), (080), (160), (061), (170), (071), and, even (0 10 0) bending states, and their resonating partners were assigned in the spectra that gives the experimental energy levels lying near or above the potential energy barrier to linearity. The assignments were confirmed by combination differences and simultaneous observation of both perturbed and perturbing levels. It was found that the high-order resonances with large changing of vibration quantum numbers are typical for the water molecule and they are caused by the strong centrifugal distortion near the linear configuration. These resonances destroy the usual polyad scheme originating from well-known Coriolis, Darling-Dennison, and Fermi resonances in H(2)O molecule. Copyright 2001 Academic Press.

The nu(1) and nu(3) Bands of the (17)O(16)O(17)O Isotopomer of Ozone.

Using 0.002 cm(-1) resolution Fourier transform absorption spectra of an (17)O-enriched ozone sample, an extensive analysis of the nu(3) band together with a partial identification of the nu(1) band of the (17)O(16)O(17)O isotopomer of ozone has been performed for the first time. As for other C(2v)-type ozone isotopomers [J.-M. Flaud and R. Bacis, Spectrochim. Acta, Part A 54, 3-16 (1998)], the (001) rotational levels are involved in a Coriolis-type resonance with the levels of the (100) vibrational state. The experimental rotational levels of the (001) and (100) vibrational states have been satisfactorily reproduced using a Hamiltonian matrix which takes into account the observed rovibrational resonances. In this way precise vibrational energies and rotational and coupling constants were deduced and the following band centers nu(0)(nu(3)) = 1030.0946 cm(-1) and nu(0)(nu(1)) = 1086.7490 cm(-1) were obtained for the nu(3) and nu(1) bands, respectively. Copyright 2000 Academic Press.

High-Lying Rotational Levels of Water: Comparison of Calculated and Experimental Energy Levels for (000) and (010) up to J = 25 and 21.

Emission spectra of methane-oxygen low-pressure flames have been recorded at a resolution of 0.02 cm-1 with an infrared Fourier transform spectrometer in the spectral ranges 780-1370 and 1800-5000 cm-1. The flame temperature was about 1850 K and a large number of transitions involving J values as high as 34 for an extended set of vibrational states could be assigned. Combined with already published data sets on H2O, our line position analysis yielded rotational energy levels for many of these states, but only the results relevant to the ground and the (010) states are presented here. The experimental energies for these two states have been fitted with the help of the bending-rotation Hamiltonian approach [L. H. Coudert, J. Mol. Spectrosc. 181, 246-273 (1997)], and for each rotational level, the calculated energy along with its uncertainty is reported and compared with the observed value. Comparisons with other available energy level data sets for the ground and (010) states are also presented. Copyright 1999 Academic Press.

Detector Nonlinearity Correction Scheme for the LPMA Balloonborne Fourier Transform Spectrometer.

The Limb Profile Monitor of the Atmosphere (LPMA) instrument is a Fourier transform spectrometer designed to record stratospheric (and in some cases tropospheric) absorption spectra from a balloon gondola. This spectrometer operates with two-detector output optics (photoconductive HgCdTe and photovoltaic InSb, liquid-nitrogen cooled). The response of the HgCdTe detector becomes nonlinear for high photon fluxes, which is the case for solar occultation. We have designed a processing scheme, based on the minimization of out-of-optical-band spectral artifacts, to correct for the effect of nonlinearity in the useful spectral range. The method is explained, and sample results are presented for spectra recorded in different balloon flight conditions and with two different HgCdTe detectors.

The Water Vapor Linestrengths between 11 600 and 12 750 cm-1

The water vapor linestrengths in the region of the 3nu + delta resonance polyad of interacting vibrational states (the corresponding upper states are (310), (211), (112), (013), (131), (230), (032), and (051)) have been analyzed leading to accurate dipole moment transition parameters. The effective rotational Hamiltonian constants used to calculate the vibration-rotation wavefunctions (J.-M. Flaud, C. Camy-Peyret, A. Bykov, O. Naumenko, T. Petrova, A. Scherbakov, L. Sinitsa, 1994. J. Mol. Spectrosc. 183, 300-309) take into account both strong centrifugal distortion effects and dark states presence. These effects are known to be important for the highly excited vibrational states of water-like molecules. The input data set included the line intensities measured by Toth (R. Toth, 1994. J. Mol. Spectrosc. 166, 176-183) and the line intensities of the weak bands 2nu1 + 3nu2, 3nu2 + 2nu3, and 3nu1 + nu2 derived from peak absorptions of a spectrum recorded at a pressure of 17.0 Torr and a path length of 434 m. The parameters of the effective dipole moment operator determined by least square fitting give a very satisfactory agreement with experimental values since the mean error for the 876 experimental linestrengths is only 3.9%. It is worth noticing that such an agreement could be reached only because high-order resonance couplings with dark states were explicitly taken into account. Copyright 1997 Academic Press. Copyright 1997Academic Press

The High-Resolution Spectrum of Water Vapor between 11 600 and 12 750 cm-1

The absorption spectrum of water vapor has been recorded between 11 600 and 12 750 cm-1 with a Fourier transform spectrometer (Kitt Peak, Az) at a resolution of 0.012 cm-1 and with a path length of 434 m. The line assignment has led to the determination of 506 accurate energy levels of the (310) (211), (112), (013), (230), (131), (032), and (051) vibrational states which belong to the so-called 3nu + delta resonance polyad. The rotational energy levels obtained are on the average in agreement with those reported recently by R. Toth (J. Mol. Spectrosc. 166, 176-183 (1994)) for the strong bands, but there are differences for high J levels or weak bands levels (about 15% of all levels). The experimental rotational energy levels have been fitted using Pade-Borel approximants and a set of 104 vibrational energies and rotational, resonance, and centrifugal distortion constants for the (310), (211), (112), (013), (230), (131), (032), and (051) vibrational states have been determined.

Rotational and vibrational dependences of collisional linewidths in the nnu(2)-(n-1)nu(2) hot bands of H2O from Fourier-transform flame spectra.

The collisional widths of ~ 160 transitions belonging mainly to the 2nu(2)-nu(2), 3nu(2)-2nu(2), and 4nu(2)-3nu(2) hot bands of the H(2)(16)O molecule have been measured on Fourier-transform air-methane flame spectra at 2000 K and analyzed, showing a strong decrease in the collisional widths when the rotational quantum number J increases, as well as a nonnegligible decrease of the collisional widths when the nu(2) vibrational quantum number increases.

Measurements of collisional linewidths in the nu(2) band of H(2)O from Fourier-transformed flame spectra.

The collisional widths of more than 200 transitions belonging to the v(2) band of the H(2)O molecule were measured by using the Fourier-transformed spectra of an air-methane flame at 2000 K. A nonlinear least-squares method was used to determine the line widths for a wide range of J (up to 28) and K(a) (up to 14) quantum number values. Finally, an analysis of the results as functions of J and K(a) is presented.

Improved line parameters for ozone bands in the 10-microm spectral region.

A complete update of spectroscopic line parameters for the 10-microm bands of ozone is reported. The listing contains calculated positions, intensities, lower state energies, and air- and self-broadened halfwidths of more than 53,000 lines. The results have been generated using improved spectroscopic parameters obtained in a number of recent high resolution laboratory studies. A total of eighteen bands of (16)O(3) (sixteen hot bands plus the nu(1) and nu(3) fundamentals) are included along with the nu(1) and nu(3) fundamentals of both (16)O(16)O(18)O and (16)O(18)O(16)O. As shown by comparisons of line-by-line simulations with 0.003-cm(-1) resolution balloon-borne stratospheric solar spectra, the new parameters greatly improve the accuracy of atmospheric calculations in the 10-microm region, especially for the isotopic (16)O(16)O(18)O and (16)O(18)O(16)O lines.

The HITRAN database: 1986 edition.

A description and summary of the latest edition of the AFGL HITRAN molecular absorption parameters database are presented. This new database combines the information for the seven principal atmospheric absorbers and twenty-one additional molecular species previously contained on the AFGL atmospheric absorption line parameter compilation and on the trace gas compilation. In addition to updating the parameters on earlier editions of the compilation, new parameters have been added to this edition such as the self-broadened halfwidth, the temperature dependence of the air-broadened halfwidth, and the transition probability. The database contains 348043 entries between 0 and 17,900 cm(-1). A FORTRAN program is now furnished to allow rapid access to the molecular transitions and for the creation of customized output. A separate file of molecular cross sections of eleven heavy molecular species, applicable for qualitative simulation of transmission and emission in the atmosphere, has also been provided.

AFGL atmospheric absorption line parameters compilation: 1982 edition.

The latest edition of the AFGL atmospheric absorption line parameters compilation for the seven most active infrared terrestrial absorbers is described. Major modifications to the atlas for this edition include updating of water-vapor parameters from 0 to 4300 cm(-1), improvements to line positions for carbon dioxide, substantial modifications to the ozone bands in the middle to far infrared, and improvements to the 7- and 2.3-microm bands of methane. The atlas now contains approximately 181,000 rotation and vibration-rotation transitions between 0 and 17,900 cm(-1). The sources of the absorption parameters are summarized.