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A Campargue - One of the best experts on this subject based on the ideXlab platform.

  • accurate measurements and temperature dependence of the water vapor self continuum absorption in the 2 1 μm Atmospheric Window
    Journal of Chemical Physics, 2015
    Co-Authors: Irene Ventrillard, A Campargue, D Mondelain, D Romanini
    Abstract:

    In spite of its importance for the evaluation of the Earth radiative budget, thus for climate change, very few measurements of the water vapor continuum are available in the near infrared Atmospheric Windows especially at temperature conditions relevant for our atmosphere. In addition, as a result of the difficulty to measure weak broadband absorption signals, the few available measurements show large disagreements. We report here accurate measurements of the water vapor self-continuum absorption in the 2.1 μm Window by Optical Feedback Cavity Enhanced Absorption Spectroscopy (OF-CEAS) for two spectral points located at the low energy edge and at the center of the 2.1 μm transparency Window, at 4302 and 4723 cm(-1), respectively. Self-continuum cross sections, CS, were retrieved with a few % relative uncertainty, from the quadratic dependence of the spectrum base line level measured as a function of water vapor pressure, between 0 and 16 Torr. At 296 K, the CS value at 4302 cm(-1) is found 40% higher than predicted by the MT_CKD V2.5 model, while at 4723 cm(-1), our value is 5 times larger than the MT_CKD value. On the other hand, these OF-CEAS CS values are significantly smaller than recent measurements by Fourier transform spectroscopy at room temperature. The temperature dependence of the self-continuum cross sections was also investigated for temperatures between 296 K and 323 K (23-50 °C). The derived temperature variation is found to be similar to that derived from previous Fourier transform spectrometer (FTS) measurements performed at higher temperatures, between 350 K and 472 K. The whole set of measurements spanning the 296-472 K temperature range follows a simple exponential law in 1/T with a slope close to the dissociation energy of the water dimer, D0 ≈ 1100 cm(-1).

  • accurate measurements and temperature dependence of the water vapor self continuum absorption in the 2 1 μm Atmospheric Window
    Journal of Chemical Physics, 2015
    Co-Authors: Irene Ventrillard, D Mondelain, D Romanini, A Campargue
    Abstract:

    In spite of its importance for the evaluation of the Earth radiative budget, thus for climate change, very few measurements of the water vapor continuum are available in the near infrared Atmospheric Windows especially at temperature conditions relevant for our atmosphere. In addition, as a result of the difficulty to measure weak broadband absorption signals, the few available measurements show large disagreements. We report here accurate measurements of the water vapor self-continuum absorption in the 2.1 μm Window by Optical Feedback Cavity Enhanced Absorption Spectroscopy (OF-CEAS) for two spectral points located at the low energy edge and at the center of the 2.1 μm transparency Window, at 4302 and 4723 cm−1, respectively. Self-continuum cross sections, CS, were retrieved with a few % relative uncertainty, from the quadratic dependence of the spectrum base line level measured as a function of water vapor pressure, between 0 and 16 Torr. At 296 K, the CS value at 4302 cm−1 is found 40% higher than pre...

  • the absorption spectrum of water vapor in the 1 25 μm Atmospheric Window 7911 8337 cm 1
    Journal of Quantitative Spectroscopy & Radiative Transfer, 2015
    Co-Authors: A Campargue, S N Mikhailenko, Benoit Guillo Lohan, E V Karlovets, D Mondelain, S Kassi
    Abstract:

    Abstract The absorption spectrum of water vapor in “natural” isotopic abundance has been recorded at room temperature by high sensitivity Continuous Wave Cavity Ring Down Spectroscopy (CW-CRDS) between 7911 and 8337 cm −1 . The investigated region covers most of the 1.25 µm transparency Window of importance for Atmospheric applications. The recordings were performed with sensitivity on the order of α min ~2×10 –11  cm −1 , more than two orders of magnitude better than previous investigations by Fourier Transform Spectroscopy (FTS). Measured line intensities cover a range of seven orders of magnitude (3×10 –30 –2×10 –23  cm/molecule at room temperature). The experimental line list provided as Supplementary Material includes more than 5000 transitions. As a result of the achieved sensitivity, more than 1150 lines of the experimental list were identified as being due to ammonia present as an impurity at the 5 ppm concentration level in the water sample. Although incomplete, the obtained ammonia line list seems to be the first one in the region. More than 3193 water lines were assigned to 3560 transitions of five water isotopologues (H 2 16 O, H 2 18 O, H 2 17 O, HD 16 O and HD 18 O). The assignments were performed using known experimental energy levels and calculated spectra based on variational calculations by Schwenke and Partridge. The obtained results are compared to the most relevant previous studies by Fourier Transform Spectroscopy in the region and to the exhaustive review of rovibrational line positions and levels performed recently by an IUPAC sponsored task group. Two-hundred and sixty-six levels are newly determined and 46 are corrected by more than 0.015 cm −1 compared to those recommended by the water IUPAC task group. The overall agreement between variational and measured intensities is satisfactory. A complete empirical list of 4473 transitions incorporating all the experimental information at disposal was constructed for water in the studied region. The intensity cut-off was fixed to 1×10 –29  cm/molecule at 296 K. A detailed comparison with the line list as provided by the HITRAN database illustrates the advantages of the new list.

  • high sensitivity cw cavity ring down spectroscopy of water in the region of the 1 5 μm Atmospheric Window
    Journal of Molecular Spectroscopy, 2004
    Co-Authors: S N Mikhailenko, S Kassi, D Romanini, P Macko, O V Naumenko, Alain Jenouvrier, Vl G Tyuterev, A Campargue
    Abstract:

    Abstract The absorption spectrum of natural water vapour around 1.5 μm has been recorded with a typical sensitivity of 5 × 10−10 cm−1 by using a CW-cavity ring down spectroscopy set up based on fibred DFB lasers. A series of 31 DFB lasers has allowed a full coverage of the 6130.8–6748.5 cm−1 (1.63–1.48 μm) region corresponding to the H transparency band of the atmosphere. The line parameters (wavenumber and intensity) of a total of 5190 lines, including 4247 lines of water vapor, were derived by a one by one fit of the lines to a Voigt profile. Different isotopologues of water (H216O, H218O, H217O, and HD16O) present in natural abundance in the sample contribute to the spectrum. For the main isotopologue, H216O, 2130 lines were measured with line intensities as weak as 10−29 cm/molecule while only 926 lines (including a proportion of 30% inaccurate calculated lines) with a minimum intensity of 3 × 10−27 cm/molecule are provided by the HITRAN and GEISA databases. Our comparison in the whole 5750–7965 cm−1 region, has also evidenced that an error in the process of conversion of the intensity units from cm−2/atm to cm−1/(molecule × cm−2) at 296 K, has led to H216O line intensities values listed in the HITRAN-2000 database, systematically 8 % below the original FTS values. The rovibrational assignment was performed on the basis of the ab initio calculations by Schwenke and Partridge with a subsequent refinement and validation using the Ritz combination principle together with all previously measured water transitions relevant to this study. This procedure allowed determining 172, 139, 71, and 115 new energy levels for the H216O, H218O, H217O, and HD16O isotopologues, respectively. The results are compared with the available databases and discussed in regard of previous investigations by Fourier transform spectroscopy. The spectrum analysis has showed that most of the transitions which cannot be assigned to water are very weak and are due to impurities such as carbon dioxide and ammonia, leaving only about 3% of the observed transitions unassigned. The interest of a detailed knowledge of water absorption for trace detectors developed in the 1.5 μm range is underlined: for instance HDO contributes significantly to the considered spectrum while no HDO line parameters are provided by the HITRAN database.

A Bauer - One of the best experts on this subject based on the ideXlab platform.

  • absorption of a h2o co2mixture in the Atmospheric Window at 239 ghz h2o co2linewidths and continuum
    Journal of Molecular Spectroscopy, 1996
    Co-Authors: A Bauer, M Godon, J Carlier, Robert R Gamache
    Abstract:

    Absolute absorption rates of mixtures of water vapor and carbon dioxide have been measured at 239 GHz which is in an Atmospheric Window for the rotational and vibrational spectra of both species. The dependence on pressure as well as temperature has been obtained. The experimental data are compared with models using conventional lineshapes. As these models require the knowledge of the collisional linewidths of the H2O broadened by CO2, theoretical calculations using the Robert–Bonamy formalism have been carried out. A very large “continuum effect” is observed when comparing the experimental absorption with the models, as well for the magnitude of the absorption discrepancy and for the strong temperature dependence of this absorption. Collision induced absorption (CIA) has also been measured at this frequency. These results can be applied to planetary observations.

  • water vapor absorption in the Atmospheric Window at 239 ghz
    Journal of Quantitative Spectroscopy & Radiative Transfer, 1995
    Co-Authors: A Bauer, M Godon, J Carlier
    Abstract:

    Absolute absorption rates of pure water vapor and mixtures of water vapor and nitrogen have been measured in the Atmospheric Window at 239 GHz. The dependence on pressure as well as temperature has been obtained. The experimental data are compared with several theoretical or empirical models, and satisfactory agreement is obtained with the models involving a continuum; in the case of pure water vapor, the continuum contribution based upon recent theoretical developments gives good results. The temperature dependence is stronger than that proposed in a commonly used Atmospheric transmission model.

  • laboratory studies of water vapor absorption in the Atmospheric Window at 213 ghz
    Journal of Quantitative Spectroscopy & Radiative Transfer, 1992
    Co-Authors: M Godon, J Carlier, A Bauer
    Abstract:

    Abstract Absolute absorption rates of water vapor have been measured in the Atmospheric Window between the rotational lines at 183 and 321–325 GHz. Measurements have been carried out for pure water vapor and mixtures with N2 at Atmospheric pressure. Pressure and temperature dependences are compared with models involving different lineshapes and different types of continua.

Alexander J Lind - One of the best experts on this subject based on the ideXlab platform.

  • mid infrared frequency comb generation and spectroscopy with few cycle pulses and χ 2 nonlinear optics
    Physical Review Letters, 2020
    Co-Authors: Alexander J Lind, Abijith S Kowligy, Henry Timmers, Flavio C Cruz, Nima Nader, Myles C Silfies, Thomas K Allison
    Abstract:

    The mid-infrared Atmospheric Window of $3--5.5\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$ holds valuable information regarding molecular composition and function for fundamental and applied spectroscopy. Using a robust, mode-locked fiber-laser source of $l11\text{ }\mathrm{fs}$ pulses in the near infrared, we explore quadratic (${\ensuremath{\chi}}^{(2)}$) nonlinear optical processes leading to frequency comb generation across this entire mid-infrared Atmospheric Window. With experiments and modeling, we demonstrate intrapulse difference frequency generation that yields few-cycle mid-infrared pulses in a single pass through periodically poled lithium niobate. Harmonic and cascaded ${\ensuremath{\chi}}^{(2)}$ nonlinearities further provide direct access to the carrier-envelope offset frequency of the near infrared driving pulse train. The high frequency stability of the mid-infrared frequency comb is exploited for spectroscopy of acetone and carbonyl sulfide with simultaneous bandwidths exceeding 11 THz and with spectral resolution as high as $0.003\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}1}$. The combination of low noise and broad spectral coverage enables detection of trace gases with concentrations in the part-per-billion range.

J Carlier - One of the best experts on this subject based on the ideXlab platform.

  • absorption of a h2o co2mixture in the Atmospheric Window at 239 ghz h2o co2linewidths and continuum
    Journal of Molecular Spectroscopy, 1996
    Co-Authors: A Bauer, M Godon, J Carlier, Robert R Gamache
    Abstract:

    Absolute absorption rates of mixtures of water vapor and carbon dioxide have been measured at 239 GHz which is in an Atmospheric Window for the rotational and vibrational spectra of both species. The dependence on pressure as well as temperature has been obtained. The experimental data are compared with models using conventional lineshapes. As these models require the knowledge of the collisional linewidths of the H2O broadened by CO2, theoretical calculations using the Robert–Bonamy formalism have been carried out. A very large “continuum effect” is observed when comparing the experimental absorption with the models, as well for the magnitude of the absorption discrepancy and for the strong temperature dependence of this absorption. Collision induced absorption (CIA) has also been measured at this frequency. These results can be applied to planetary observations.

  • water vapor absorption in the Atmospheric Window at 239 ghz
    Journal of Quantitative Spectroscopy & Radiative Transfer, 1995
    Co-Authors: A Bauer, M Godon, J Carlier
    Abstract:

    Absolute absorption rates of pure water vapor and mixtures of water vapor and nitrogen have been measured in the Atmospheric Window at 239 GHz. The dependence on pressure as well as temperature has been obtained. The experimental data are compared with several theoretical or empirical models, and satisfactory agreement is obtained with the models involving a continuum; in the case of pure water vapor, the continuum contribution based upon recent theoretical developments gives good results. The temperature dependence is stronger than that proposed in a commonly used Atmospheric transmission model.

  • laboratory studies of water vapor absorption in the Atmospheric Window at 213 ghz
    Journal of Quantitative Spectroscopy & Radiative Transfer, 1992
    Co-Authors: M Godon, J Carlier, A Bauer
    Abstract:

    Abstract Absolute absorption rates of water vapor have been measured in the Atmospheric Window between the rotational lines at 183 and 321–325 GHz. Measurements have been carried out for pure water vapor and mixtures with N2 at Atmospheric pressure. Pressure and temperature dependences are compared with models involving different lineshapes and different types of continua.

O J Nielsen - One of the best experts on this subject based on the ideXlab platform.

  • relative integrated ir absorption in the Atmospheric Window is not the same as relative radiative efficiency
    Proceedings of the National Academy of Sciences of the United States of America, 2010
    Co-Authors: Timothy J Wallington, Mads Sulbaek P Andersen, O J Nielsen
    Abstract:

    In their paper “Design strategies to minimize the radiative efficiency of global warming molecules,” Bera et al. (1) mistakenly equate the relative magnitudes of integrated absorption within the Atmospheric Window (800–1,400 cm−1) with relative radiative efficiencies of different molecules. Radiative efficiency is defined as the change in net radiation at the tropopause caused by a given change in greenhouse gas concentration or mass and has units of W·m−2·ppb−1 (2, 3). Radiative efficiency is calculated using radiative transfer models of the atmosphere and depends on the strength and spectral position of a compound's absorption bands, Atmospheric structure, surface temperature, and presence or absence of clouds (2, 3). The Atmospheric Window is a region in the infrared where the Earth's atmosphere is relatively transparent, through which blackbody radiation from Earth's surface can escape to space, thereby cooling the planet. Species with long Atmospheric lifetimes (years) and that absorb strongly in the Atmospheric Window have a particularly pronounced contribution to radiative forcing of climate change (Fig. 1).

  • relative integrated ir absorption in the Atmospheric Window is not the same as relative radiative efficiency
    Proceedings of the National Academy of Sciences of the United States of America, 2010
    Co-Authors: Timothy J Wallington, M Sulbaek P Andersen, O J Nielsen
    Abstract:

    In their paper “Design strategies to minimize the radiative efficiency of global warming molecules,” Bera et al. (1) mistakenly equate the relative magnitudes of integrated absorption within the Atmospheric Window (800–1,400 cm−1) with relative radiative efficiencies of different molecules. Radiative efficiency is defined as the change in net radiation at the tropopause caused by a given change in greenhouse gas concentration or mass and has units of W·m−2·ppb−1 (2, 3). Radiative efficiency is calculated using radiative transfer models of the atmosphere and depends on the strength and spectral position of a compound's absorption bands, Atmospheric structure, surface temperature, and presence or absence of clouds …