Transfert de charge de protons avec formation d'atomes d'hydrogène fortement excités

A study was made of the formation of highly excited hydrogen atoms, having principal quantum numbers n ≽ 9, by charge exchange of 20-150 keV protons in the gases H2, Ar, He. The relative yield of highly excited atoms was determined by ionizing them in a strong electric field. It was found a maximum for the yield of these atoms at the same order of the energy, in the case of H2 and Ar.On étudie la formation d'atomes d'hydrogène excités sur des niveaux n ≽ 9, par échange de charge de protons d'énergie 20 à 150 keV, passant à travers différents gaz : H2, Ar, He. La production relative des atomes excités est déterminée par leur ionisation au moyen d'un champ électrique intense. Les résultats montrent que la production maximale d'atomes excités est obtenue pour la même valeur de l'énergie des ions, dans le cas où l'échange de charge se fait avec des gaz hydrogène et d'argon

Sections efficaces d'émission des raies de Balmer Hα, H β, Hγ produites par impact de protons 10-100 keV sur N2 et O2

Absolute cross sections have been measured for the emission of the Balmer Hα, Hβ, Hγ lines produced by 10-100 keV proton impact on N2 and O2. The polarization of the Hα and Hβ lines has been determined for these gases from 10 to 60 keV. The cross sections show a similar dependence on impact energy for different lines, except at low energy for Hβ and Hγ in N2.Nous avons mesuré des valeurs absolues des sections efficaces d'émission des raies de Balmer Hα, Hβ, Hγ produites par collisions de protons d'énergie 10 keV ≤ E ≤ 100 keV sur les cibles N2 et O2. La polarisation des raies Hα et Hβ a été déterminée pour 10 keV ≤ E ≤ 60 keV. Les sections efficaces montrent une même dépendance en fonction de l'énergie pour les différentes raies, excepté à basse énergie pour les raies Hβ et Hγ dans N2

Uniform Supersonic Expansion for FTIR Absorption Spectroscopy: The ν5 Band of (NO)2 at 26 K

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Estimation of line parameters under line mixing effect: the nu3 band of CH4 in helium

International audienceSpectra of CH4-He mixtures were measured in the P and R branch regions of nu3 vibration-rotation band at lower pressures of 0.26-1.0 bar and for the whole band at higher pressures up to 90 bar. The line broadening coefficients were found from lower pressure data for the lines of the P branch. These coefficients were calculated in the framework of the Robert and Bonamy semi-classical approach. In general, they agree with the experimental ones, but a small J-dependent deviation was observed. Line mixing effects were observed at all pressures. At higher pressures they were interpreted in terms of the adjusted branch-coupling model. At lower pressures line mixing effects were found to be especially pronounced in the region of the relatively weak lines forming the clusters from R(16) to R(19)

Absorption of radiation by gases from low to high pressures. II. Measurements and calculations of CO infrared spectra

This paper presents tests of the models developed in a first paper [J. Phys. II France 1 (1991) 739] when applied to CO infrared spectra. New measurements at high densities and temperatures are presented. Comparisons between experimental and calculated results confirm the inaccuracy of the Lorentz and low density statistical approaches when line-mixing and far linewings make significant contributions to absorption. On the other hand, the empirical models proposed in paper I lead to a satisfactory agreement with the values measured. Tabulations of data suitable for the Generalized Narrow Band Statistical Model are given, which enable easy and quick computations for practical applications.Cet article présente des applications des modèles développés dans une première publication [J. Phys. II France 1 (1991) 739] au calcul de spectres infrarouge de CO. Des mesures nouvelles à température et pression élevées sont aussi présentées. Les résultats expérimentaux et théoriques confirment l'imprécision de l'approche Lorentz ainsi que des modèles statistiques basse densité lorsque les effets d'interférence entre raies et les ailes lointaines contribuent notablement à l'absorption. En revanche, les modèles empiriques corrigés proposés dans l'article I donnent des résultats satisfaisants. Des tables de paramètres adaptés pour le modèle de bande généralisé, qui sont données dans le présent travail, permettent, pour des applications pratiques, un calcul facile et rapide

Line parameters and shapes of high clusters: R-branch of the nu3 band of CH4 in He mixtures

International audienceThe IR absorption spectra of CH4 in pure gas and in mixture with helium were studied in the region of nu3 band at higher J line clusters R(17)-R(22). The frequencies and intensities of rotation-vibration lines were estimated from the experimental spectra at Doppler shape conditions. The line frequencies and intensities were calculated and used for the attribution of overlapped lines in clusters. The calculated line intensities are close to the experimental values. The calculated frequency structure of the higher J manifolds are somewhat wider than the observed one. The shapes of helium-broadened line clusters were compared with those calculated accounting for line mixing. The relaxation matrix W, which is necessary in shape calculations, was constructed using semiclassical collision rate constants. The calculated shapes are in satisfactory accordance with the measured ones

Experimental and theoretical study of line mixing in methane spectra. II. Influence of the collision partner (He and Ar) in the v3 IR band

Line mixing effects are studied in the v3 band of CH4 perturbed by Ar and He at room temperature. Experiments have been made in the 2800-3200 cm-1 spectral region using four different setups. They cover a wide range of total densities, including low (0.25-2 atm), medium (25-100 atm), and high (200-1000 atm) pressure conditions. Analysis of the spectra demonstrates that the spectral shapes (of the band, the Q branch, the P and R manifolds,...) are significantly influenced by line mixing. The theoretical approach proposed in the preceding paper is used in order to model and analyze these effects. As done previously, semiclassical state-to-state rates are used together with a few empirical constants. Comparisons between measurements and spectra computed with and without the inclusion of line mixing are made. They prove the quality of the approach which satisfactorily accounts for the effects of pressure and of rotational quantum numbers on the spectral shape. It is shown that collisions with He and Ar lead to different line-coupling schemes (e.g., more coupling within the branches and less between branches) and hence to different shapes. The influence of line coupling between different branches and manifolds is evidenced and studied using high pressure spectra and absorption in the band wings. © 1999 American Institute of Physics.Peer Reviewe