Showing papers by "Vincent Boudon published in 2011"

The 2009 edition of the GEISA spectroscopic database

Abstract: The updated 2009 edition of the spectroscopic database GEISA (Gestion et Etude des Informations Spectroscopiques Atmospheriques; Management and Study of Atmospheric Spectroscopic Information) is described in this paper. GEISA is a computer-accessible system comprising three independent sub-databases devoted, respectively, to: line parameters, infrared and ultraviolet/visible absorption cross-sections, microphysical and optical properties of atmospheric aerosols. In this edition, 50 molecules are involved in the line parameters sub-database, including 111 isotopologues, for a total of 3,807,997 entries, in the spectral range from 10−6 to 35,877.031 cm−1. The successful performances of the new generation of hyperspectral sounders depend ultimately on the accuracy to which the spectroscopic parameters of the optically active atmospheric gases are known, since they constitute an essential input to the forward radiative transfer models that are used to interpret their observations. Currently, GEISA is involved in activities related to the assessment of the capabilities of IASI (Infrared Atmospheric Sounding Interferometer; http://smsc.cnes.fr/IASI/index.htm) on board the METOP European satellite through the GEISA/IASI database derived from GEISA. Since the Metop-A (http://www.eumetsat.int) launch (19 October 2006), GEISA is the reference spectroscopic database for the validation of the level-1 IASI data. Also, GEISA is involved in planetary research, i.e., modeling of Titan's atmosphere, in the comparison with observations performed by Voyager, or by ground-based telescopes, and by the instruments on board the Cassini–Huygens mission. GEISA, continuously developed and maintained at LMD (Laboratoire de Meteorologie Dynamique, France) since 1976, is implemented on the IPSL/CNRS (France) “Ether” Products and Services Centre WEB site (http://ether.ipsl.jussieu.fr), where all archived spectroscopic data can be handled through general and user friendly associated management software facilities. More than 350 researchers are registered for on line use of GEISA.

Spherical Top Theory and Molecular Spectra

Abstract: In this article, we present an overview of the present state of the art of the theory of high-resolution spherical-top spectra in the framework of the effective Hamiltonian approach. We describe the specific features of this class of molecules to explain the basic concepts of the theoretical methods used for the analysis (line positions and intensities) and the simulation of absorption (including pure rotation) and Raman spectra of such species. The non conventional formalism that we use is essentially based on irreducible tensor methods and is especially adapted to computational treatments and global analyses of complex interacting band systems. We give examples concerning mainly methane (CH4) and sulfur hexafluoride (SF6). The efficiency of these methods is not restricted to spherical tops, as they also apply to other molecular species or spectroscopic problems. We demonstrate this through recent developments including the modeling of the effects of collisions on line shapes, the modeling of rovibronic effects, as well as extensions to molecules with lower symmetry. The computer implementation of the methods is an integral part of the modeling. We conclude the article with an overview of the free access programs and databases developed in the Dijon group for spherical-top molecules and some other species. Keywords: spherical tops; rovibrational spectroscopy; group theory; tensorial formalism; vibrational polyads; methane; sulfur hexafluoride; collisional broadening; extension to lower symmetries; rovibronic spectra; programs and databases

High-Resolution Spectroscopy and Preliminary Global Analysis of C-H Stretching Vibrations of C2H4 in the 3000 and 6000 cm-1 Regions

Abstract: Abstract Ethylene (ethene, H2C=CH2) is a naturally occurring compound in ambient air that affects atmospheric chemistry and global climate. The C2H4 spectrum is available in databases only for the 1000 and 3000 cm−1 ranges. In this work, the ethylene absorption spectrum was measured in the 6030–6250 cm−1 range with the use of a high resolution Bruker IFS 125HR Fourier-spectrometer and a two-channel opto-acoustic spectrometer with a diode laser. As a secondary standard of wavelengths, the methane absorption spectrum was used in both cases. A preliminary analysis was realized thanks to the tensorial formalism developed by the Dijon group that is implemented in the XTDS software package [39] . We considered the two combination bands ν 5 + ν 9 and ν 5 + ν 11 as an interacting dyad. Parameters for the ν 9 / ν 11 dyad were fitted simultaneously from a re-analysis of previously recorded supersonic expansion jet FTIR data, while parameters for the v5=1 Raman level were taken from literature. More than 600 lines could be assigned in the 6030–6250 cm−1 region (and also 682 in the 2950–3150 cm−1 region) and effective Hamiltonian parameters were fitted, including Coriolis interaction parameters. The dyad features are globally quite well reproduced, even if there are still problems at high J values.

VAMDC - The Virtual Atomic and Molecular Data Centre - A new way to disseminate atomic and molecular data - VAMDC level 1 release

Abstract: The Virtual Atomic and Molecular Data Centre (VAMDC, http://www.vamdc.eu/) is a European‐Union‐funded collaboration between groups involved in the generation, evaluation, and use of atomic and molecular data. VAMDC aims to build a reliable, open, flexible and interoperable e‐science interface to existing atomic and molecular data. The project will cover establishing the core consortium, the development and deployment of the infrastructure and the development of interfaces to the existing atomic and molecular databases. This paper describes the organisation of the project and the achievements during its first year.

ON THE VOLATILE ENRICHMENTS AND HEAVY ELEMENT CONTENT IN HD189733b

Abstract: Favored theories of giant planet formation center around two main paradigms, namely the core accretion model and the gravitational instability model. These two formation scenarios support the hypothesis that the giant planet metallicities should be higher or equal to that of the parent star. Meanwhile, spectra of the transiting hot Jupiter HD189733b suggest that carbon and oxygen abundances range from depleted to enriched with respect to the star. Here, using a model describing the formation sequence and composition of planetesimals in the protoplanetary disk, we determine the range of volatile abundances in the envelope of HD189733b that is consistent with the 20-80 M⊕ of heavy elements estimated to be present in the planet's envelope. We then compare the inferred carbon and oxygen abundances to those retrieved from spectroscopy, and we find a range of supersolar values that directly fit both spectra and internal structure models. In some cases, we find that the apparent contradiction between the subsolar elemental abundances and the mass of heavy elements predicted in HD189733b by internal structure models can be explained by the presence of large amounts of carbon molecules in the form of polycyclic aromatic hydrocarbons and soots in the upper layers of the envelope, as suggested by recent photochemical models. A diagnostic test that would confirm the presence of these compounds in the envelope is the detection of acetylene. Several alternative hypotheses that could also explain the subsolar metallicity of HD189733b are formulated: the possibility of differential settling in its envelope, the presence of a larger core that did not erode with time, a mass of heavy elements lower than the one predicted by interior models, a heavy element budget resulting from the accretion of volatile-poor planetesimals in specific circumstances, or the combination of all these mechanisms.

High-resolution spectroscopy and analysis of the ν3/2ν4 dyad of CF4

Abstract: CF4 is a strong greenhouse gas of both anthropogenic and natural origin [D.R. Worton et al., Environ. Sci. Technol. 41, 2184 (2007)]. However, high-resolution infrared spectroscopy of this molecule has received only a limited interest up to now. Until very recently, the public databases only contained cross-sections for this species, but no detailed line list. We reinvestigate here the strongly absorbing ν3 region around 7.8 μm. New Fourier transform infrared (FTIR) spectra up to a maximal resolution of 0.0025 cm−1 have been recorded: (i) room-temperature spectra in a static cell and (ii) a supersonic expansion jet spectrum at a 23 K estimated temperature. Following the work of Gabard et al. [Mol. Phys. 85, 735 (1995)], we perform a simultaneous analysis of both the ν3 and 2ν4 bands since a strong Coriolis interaction occurs between them, perturbing the ν3 R-branch rotational clusters around J = 20. Similarly to Gabard et al. , we also include ν4 FTIR data and microwave data in the fit. The analysis is pe...

Near-infrared radiative transfer modelling with different CH4 spectroscopic databases to retrieve atmospheric methane total amount

Abstract: Atmospheric methane content can be retrieved from measurements of solar radiation attenuated by the atmosphere in the near infrared spectral region where the space-borne and ground-based spectrometers carry out regular measurements. It is shown, in the present work, that the different spectroscopic databases can give significantly different results for both forward simulations of the atmospheric transmittance and the inverse problem solution to retrieve the CH 4 total content in the atmosphere using spectra measured by ground-based FTIR spectrometer in the near infrared spectral region. These discrepancies and the problem of the reduction of their influence on the atmospheric radiation transfer calculations are discussed. A comparison of atmospheric ground-based measured and simulated spectra, modelled with different CH 4 databases, is presented.

High resolution spectroscopy and global analysis of the tetradecad region of methane ${}^{12}$ch$_4$

Abstract: Author Institution: Institute of Atmospheric Optics, 634055 Tomsk, Russia and Laboratoire GSMA, UMR 6089 CNRS-Universite de Reims Champagne Ardenne, Moulin de la Housse BP 1039, Cases 16-17, F-51687 Reims Cedex 2, France; Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 5209 CNRS-Universite de Bourgogne, 9. Av. A. Savary, BP 47870, F-21078 Dijon Cedex, France; Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109, USA; Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland and Institut fur Physikalische und Theoretische Chemie, Technische Universitat Braunschweig, D-38106, Germany; Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland

22nd Colloquium on High Resolution Molecular Spectroscopy: Special Issue dedicated to Gianfranco Di Lonardo

Abstract: This issue, together with a second issue to appear in early 2012, consists of contributions submitted by participants attending the Colloquium on High Resolution Molecular Spectroscopy (HRMS), held...

D2hTDS-ST software for Stark spectrum simulation of X2Y4 asymmetric-top molecules

Abstract: We present the D 2 h TDS-ST ( D 2 h -Top Data System for Stark effect) program suite with the aim to simulate Stark spectra of any IR active rovibrational polyad of X 2 Y 4 ( D 2 h ) asymmetric-top molecules. D 2 h TDS-ST consists in a series of FORTRAN programs called by scripts. For calculation of Stark spectra, we obtained the expressions of the dipole moment and polarizability operators of X 2 Y 4 molecules using a tensorial formalism. For convenience, we integrated the D 2 h TDS-ST programs into the D 2 h TDS package. The D 2 h TDS suite (including the D 2 h TDS-ST programs) is freely available at the URL: http://icb.u-bourgogne.fr/OMR/SMA/SHTDS/D2HTDS.html .

High-resolution spectroscopy and analysis of the nu3/2nu4 dyad of CF4

Abstract: CF4 is a strong greenhouse gas of both anthropogenic and natural origin [D.R. Worton et al., Environ. Sci. Technol. 41, 2184 (2007)]. However, high-resolution infrared spectroscopy of this molecule has received only a limited interest up to now. Until very recently, the public databases only contained cross-sections for this species, but no detailed line list. We reinvestigate here the strongly absorbing ν3 region around 7.8 μm. New Fourier transform infrared (FTIR) spectra up to a maximal resolution of 0.0025 cm−1 have been recorded: (i) room-temperature spectra in a static cell and (ii) a supersonic expansion jet spectrum at a 23 K estimated temperature. Following the work of Gabard et al. [Mol. Phys. 85, 735 (1995)], we perform a simultaneous analysis of both the ν3 and 2ν4 bands since a strong Coriolis interaction occurs between them, perturbing the ν3 R-branch rotational clusters around J = 20. Similarly to Gabard et al. , we also include ν4 FTIR data and microwave data in the fit. The analysis is performed thanks to the XTDS and SPVIEW programs [Ch. Wenger et al., J. Mol. Spectrosc., 251 102 (2008)]. Compared to Gabard et al. , the present work extends the analysis up to higher J values (56 instead of 32). Absorption intensities are estimated thanks to the dipole moment derivative from D. Papousek et al. [J. Phys. Chem. 99, 15387 (1995)] and compare well with the experiment. We have produced a synthetic linelist that is included in the HITRAN 2008 and GEISA 2009 public databases. The rotational energy surfaces for the dyad are also examined in detail in order to understand the distribution and clustering patterns of rovibrational levels.