Transferts rotationnels induits par collisions dans les systemes NH_3-H_2 et NH_3-He

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Air-induced collisional parameters in the ν3 band of methane

Air broadening and shift coefficients together with narrowing and first order line mixing parameters were measured for 166 lines belonging to J″ manifolds of the P (J″=2−11), Q (J″=1−12) and R (J″=0−11) branches of the ν3 band of 12CH4 near 3.3 μm. These measurements were carried out using a non-linear multispectrum least squares fitting technique. A hard collision Dicke narrowed line shape model including Rosenkranz line mixing was applied. Five high resolution Fourier transform spectra were recorded at room temperature, one at low pressure with pure methane and four at pressures up to 904 hPa with mixtures of methane and air. The measured parameters are compared with data available in the literature.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Raman spectra in LiH2PO4 and KLi(H2PO4)2: Mode assignement

International audienceWe report and analyze Raman spectra recorded on crystals of LiH2PO4 (LDP) and KLi(H2PO4)2 (KLDP). We provide a new and complete assignment of Raman lines in both crystals from their behavior as function of temperature. Among internal vibrations, we discern the modes within PO4 tetrahedra, the modes related to Li―O bonds, and those due to the O―H vibrations. In the wavenumber range between 300 and 600 cm−1, the lines associated with O―P―O or Li―O show different temperature dependencies. The bands of PO4 are red‐shifted with increasing temperature according to thermal dilatation, whereas the positions related to Li―O are temperature independent

Phase transformations in LiH2PO4 (LDP) revealed by Raman spectroscopy

International audienceWe investigate Raman scattering measurements on polycrystalline LiH2PO 4 (LDP) between 30 and 240°C, in order to detect phase transformations. The thermal behavior of main lines in different wavenumber ranges is discussed and analyzed. Raman spectra show two anomalies at 176°C and 210°C, reflecting changes in chemical bonds, and are attributed to progressive polymerization, in agreement with earlier electrical measurements

Measured and calculated O2-broadening coefficients of C2H4 in the 1800–2350 cm-1 spectral region

International audienc

Analysis of the rotationally-resolved 3.3 µm region of C2H4 in natural isotopic abundance

International audienceEthylene (or ethene) is a natural gas compound present in our atmosphere but also in the atmospheres of outer solar system planets such as Jupiter, Saturn, Uranus, Neptune and Saturn’s moon Titan. However, a better knowledge of spectroscopic parameters is needed for this molecule in order to detect its presence and/or to derive its accurate concentration. We present here a detailed analysis and modeling of the strongly absorbing ν9 and ν11 fundamental bands in the 3.3 µm region. Due to the complexity of the observed spectrum, we have built a polyad scheme taking into account some fundamental bands previously analyzed thanks to the tensorial formalism developed in Dijon for asymmetric-top molecules. A four polyad system has been settled and the last P3 polyad contains five vibrational states: ν9, ν11, ν2 + ν12 and 2ν10 + ν12. A first frequency analysis has been performed, leading to 3328 assignments with a root mean square of 5.927 ´10−3 cm−1 and a standard deviation of 1.965 using 88 adjusted parameters, and we have also adjusted line intensities of 2190 lines by adjusting 14 parameters with an overall Root-Mean-Square (RMS) deviation of about 3.77%. A new linelist of calculated lines in the 2900 − 3300 cm−1 region has been added to the ECaSDa and we plan to integrate it to t h e HITRAN database

Line parameters measurements and modeling for the ν6 band of CH3I: A complete line list for atmospheric databases

International audienceThe present work is dedicated to the ν6 band of 12CH3I with the aim of generating a complete line list for databases. High resolution Fourier transform spectra have been recorded in MONARIS and a multispectrum fitting procedure using Voigt profile has been applied to retrieve line positions, intensities, and self-broadening coefficients for around 1200 transitions of the ν6 band between 854 and 963 cm−1. Rotational dependences of transition dipole moment squared and self-widths have been studied and empirically modeled. Line positions are retrieved with accuracy equal to 4.10−4 cm−1. The accuracy of line intensities and self-widths measurements is estimated between 5 and 10 %. Theoretical estimates of CH3I self-broadening coefficients for large ranges of rotational quantum numbers (0 ≤ J ≤ 70, 0 ≤ K ≤ 20) are also provided in the frame of a semi-classical approach with exact trajectories and of a semi-empirical method including a correction factor to the Anderson-type line-width expression. Comparisons of our results with the data previously published in the literature are presented and discussed. A complete line list of 5787 transitions is generated. Available as supplementary material, this line list can be used for spectroscopic databases and atmospheric or industrial detection of CH3I