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Accueil > Équipes scientifiques > Systèmes Moléculaires, Astrophysique et Environnement (SYSTEMAE) > Publications > 2021
2021
Peer-reviewed Publications |
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Boulet, C., & Hartmann, J. - M. (2021). Toward measurements of the speed-dependence of line-mixing. Journal of Quantitative Spectroscopy and Radiative Transfer, .
Résumé: We theoretically demonstrate that some doublets of NH3 broadened by Ar and heavier atoms may be suitable for the first experimental demonstration of a so-far unstudied problem: The spectral effects of the speed dependence of line-mixing. By using realistic assumptions and spectroscopic data from previous studies, we show that neglecting this process leads to errors on the spectral shape of up to 2% of the peak absorption value. When multispectrum fits are made assuming speed-independent line couplings, the peak-to-dip residuals amplitudes reduce to about 0.5% and 1% for NH3-Ar and -Xe, respectively. The magnitude of the effect is thus comparable to that of the speed dependence of the line broadening on isolated shapes, which has been demonstrated in many experimental studies. It should hence be detectable with high accuracy modern laboratory spectroscopic techniques. With this aim, guidelines and conditions paving the path for future experiments are given.
Mots-Clés: Speed-dependent line mixing; NH3 doublets; hard collision model
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Dartois, E., & Langlet, F. (2021). Ethane clathrate hydrate infrared signatures for solar system remote sensing. Icarus, 357, 114255.
Résumé: Hydrocarbons such as methane and ethane are present in many solar system objects, including comets, moons and planets. The interaction of these hydrocarbons with water ice at low temperatures could lead to the formation of inclusion compounds, such as clathrate hydrates (water based host cages trapping guest molecules), modifying their retention, stability and therefore evolution. The occurrence of clathrate hydrates on solar system surfaces could be established by remote sensing of their spectroscopic signatures. In this study, we measure and analyse ethane clathrate hydrate spectra recorded in the temperature range from 5.3 to 160 K, covering most of the temperature range of interest for solar system objects. Specific infrared band signatures are identified for the ethane encaged guest. We provide evidence that ethane clathrate hydrate outcrops can be detected by remote sensing on the surface of planetary bodies.
Mots-Clés: Planetary ices; IR spectroscopy; Clathrate hydrate; Ethane; Remote sensing
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Endres, C. P., Martin-Drumel, M. - A., Zingsheim, O., Bonah, L., Pirali, O., Zhang(张天惟), T., Sánchez-Monge, Á., Möller, T., Wehres, N., Schilke, P., McCarthy, M. C., Schlemmer, S., Caselli, P., & Thorwirth, S. (2021). SOLEIL and ALMA views on prototypical organic nitriles: C2H5CN. Journal of Molecular Spectroscopy, 375, 111392.
Résumé: The high resolution vibrational spectrum of ethyl cyanide (C2H5CN) has been investigated in the far-IR using synchrotron-based Fourier transform spectroscopy. The assignment was performed using the Automated Spectral Assignment Procedure (ASAP) allowing accurate rotational energy levels of the four lowest fundamental vibrations of the species, namely the v13=1 @ 205.934099(8)cm−1, v21=1 @ 212.141101(8)cm−1, v20=1 @ 372.635293(15)cm−1, and v12=1 @ 532.699617(16)cm−1 states, to be determined. The analysis not only confirms the applicability of the ASAP in the treatment of (dense) high-resolution infrared spectra but also reveals some of its limitations. Complementary to the infrared study, the pure rotational spectrum of C2H5CN was also studied in selected frequency ranges from 75 to 255GHz. New observations of a prototypical high-mass star-forming region, G327.3–0.6, performed with the Atacama Large Millimeter Array show that vibrational satellites of C2H5CN can be very intense, of order several tens of Kelvin in units of brightness temperature.
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Rojas, J., Duprat, J., Engrand, C., Dartois, E., Delauche, L., Godard, M., Gounelle, M., Carrillo-Sánchez, J. D., Pokorný, P., & Plane, J. M. C. (2021). The micrometeorite flux at Dome C (Antarctica), monitoring the accretion of extraterrestrial dust on Earth. Earth and Planetary Science Letters, 560, 116794.
Résumé: The annual flux of extraterrestrial material on Earth is largely dominated by sub-millimetre particles. The mass distribution and absolute value of this cosmic dust flux at the Earth's surface is however still uncertain due to the difficulty in monitoring both the collection efficiency and the exposure parameter (i.e. the area-time product in m2.yr). In this paper, we present results from micrometeorite collections originating from the vicinity of the CONCORDIA Station located at Dome C (Antarctica), where we performed several independent melts of large volumes of ultra-clean snow. The regular precipitation rate and the exceptional cleanliness of the snow from central Antarctica allow a unique control on both the exposure parameter and the collection efficiency. A total of 1280 unmelted micrometeorites (uMMs) and 808 cosmic spherules (CSs) with diameters ranging from 30 to 350 μm were identified. Within that size range, we measured mass fluxes of 3.0 μg.m−2.yr−1 for uMMs and 5.6 μg.m−2.yr−1 for CSs. Extrapolated to the global flux of particles in the 12-700 μm diameter range, the mass flux of dust at Earth's surface is 5,200±12001500 tons.yr−1 (1,600±500 and 3,600±7001000 tons.yr−1 of uMMs and CSs, respectively). We indicate the statistical uncertainties expected for collections with exposure parameters in the range of 0.1 up to 105 m2.yr. In addition, we estimated the flux of altered and unaltered carbon carried by heated and un-heated particles at Earth's surface. The mass distributions of CSs and uMMs larger than 100 μm are fairly well reproduced by the CABMOD-ZoDy model that includes melting and evaporation during atmospheric entry of the interplanetary dust flux. These numerical simulations suggest that most of the uMMs and CSs originate from Jupiter family comets and a minor part from the main asteroid belt. The total dust mass input before atmospheric entry is estimated at 15,000 tons.yr−1. The existing discrepancy between the flux data and the model for uMMs below 100 μm suggests that small fragile uMMs may evade present day collections, and/or that the amount of small interplanetary particles at 1 AU may be smaller than expected.
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