Physical Sciences and Mathematics Commons^™

Absolute Nitrogen Atom Density Measurements By Two-Photon Laser-Induced Fluorescence Spectroscopy In Atmospheric Pressure Dielectric Barrier Discharges Of Pure Nitrogen, Et-Touhami Es-Sebbar, Christian Sarra-Bournet, Nicolas Naudé, Françoise Massines, Nicolas Gherardi

Dr. Et-touhami Es-sebbar

In this paper, two-photon absorption laser induced fluorescence spectroscopy is used to follow the nitrogen atom density in flowing dielectric barrier discharges fed with pure nitrogen and operating at atmospheric pressure. Two different dielectric barrier discharge regimes are investigated: the Townsend regime, which is homogeneous although operating at atmospheric pressure, and the more common filamentary regime. In both regimes, densities as high as 3x1014 /cm3 are detected. However, the N atoms kinetic formation depends on the discharge regime. The saturation level is reached more rapidly with a filamentary discharge. For a given discharge regime, the N atom density depends strongly …

Contributions To The Development Of The S.E.T.U.P. (Experimental And Theoretical Simulations Useful For Planetology) Project, E. Arzoumanian, C. Romanzin, M-C. Gazeau, Et. Es-Sebbar, A. Jolly, S. Perrier, Y. Benilan

Dr. Et-touhami Es-sebbar

No abstract provided.

Multiwavelength Studies For Titan's Atmospheric Composition Analysis, Y. Benilan, Et. Es-Sebbar, N. Fray, M-C. Gazeau, A. Jolly, M. Schwell, J. Guillemin

Dr. Et-touhami Es-sebbar

Titan's atmosphere mainly made of nitrogen and methane is rich in organic molecules. Hydrocarbons are formed from the photolytic dissociation of CH4 and nitriles are created by dissociation of N2 followed by reactions with hydrocarbons. In order to understand the physicochemical mechanisms responsible for the evolution of Titan's atmosphere, photochemical models are built. The latter need constrains for vertical profiles of organic compounds from the high thermosphere down to the low stratosphere as well as photodissociation rates. Those profiles over the entire atmosphere can be retrieved from Cassini observations, in particular by limb sounding, coupling infrared and ultraviolet spectroscopy. However, …

Vuv Photostability Of Prebiotic Species, M. Schwell, Y. Bénilan, M.-C. Gazeau, N. Fray, A. Jolly, Et. Es-Sebbar, N. Champion, S. Leach, H. W Jochims, H. Baumgärtel, E. Rühl

Dr. Et-touhami Es-sebbar

No abstract provided.

S.E.T.U.P. Experimental And Theoretical Simulations Useful For Planetology- Related Studies In The Frame Of A Program Of Titan’S Atmosphere Laboratory Simulations, M.-C. Gazeau, Et. Es-Sebbar, E. Arzoumanian, C. Romanzin, A. Jolly, S. Perrier, Y. Bénilan

Dr. Et-touhami Es-sebbar

No abstract provided.

Radial Distribution Of Stars, Gas, And Dust In Sings Galaxies. Ii. Derived Dust Properties, J.C. Munoz-Mateo, A. Gil De Paz, S. Boissier, J. Zamorano, D.A. Dale, P.G. Perez-Gonzalez, Michele D. Thornley

Michele Thornley

Comet C/2004 Q2 (Machholz): Parent Volatiles, A Search For Deuterated Methane, And Constraint On The Ch4 Spin Temperature, Boncho P. Bonev, Michael J. Mumma, Erika L. Gibb, Michael A. Disanti, Geronimo L. Villanueva, Karen Magee-Sauer, Richard S. Ellis

Erika Gibb

Characterization Of An N2 Flowing Microwave Post-Discharge By Oes Spectroscopy And Determination Of Absolute Ground-State Nitrogen Atom Densities By Talif, Et. Es-Sebbar, Y. Benilan, A. Jolly, M-C. Gazeau

Dr. Et-touhami Es-sebbar

A flowing microwave post-discharge source sustained at 2.45 GHz in pure nitrogen has been investigated by optical emission spectroscopy (OES) and two-photon absorption laser-induced fluorescence (TALIF) spectroscopy. Variations of the optical emission along the post-discharge (near, pink and late afterglow) have been studied and the gas temperature has been determined. TALIF spectroscopy has been used in the late afterglow to determine the absolute ground-state nitrogen atomic densities using krypton as a reference gas. Measurements show that the microwave flowing post-discharge is an efficient source of N (4S) atoms in late afterglow. In our experimental conditions, the maximum N (4S) density …

Polarization Variability Arising From Clumps In The Winds Of Wolf-Rayet Stars., Qing-Kang Li, Joseph P. Cassinelli, John C. Brown, Richard Ignace

Richard Ignace

The polarimetric and photometric variability of Wolf-Rayet (WR) stars as caused by clumps in the winds, is revisited. In the model which is improved from Li et al. 2000, the radial expansion of the thickness is accounted for, but we retain the dependence on the beta velocity law, stellar occultation effects. We again search for parameters that can yield results consistent with observations in regards to the mean polarization, the ratio of polarimetric to photometric variability, and the volume filling factor. Clump generation and spatial distribution are randomized by the Monte Carlo method so as to produce clumps which are, …

Scattering Polarization Due To Light Source Anisotropy Ii. Envelope Of Arbitrary Shape., Richard Ignace, M. B. Al-Malki, J. F. L. Simmons, J. C. Brown, D. Clarke, J. C. Carson

Richard Ignace

Aims. We consider the polarization arising from scattering in an envelope illuminated by a central anisotropic source. This work extends the theory introduced in a previous paper (Al-Malki et al. 1999) in which scattering polarization from a spherically symmetric envelope illuminated by an anisotropic point source was considered. Here we generalize to account for the more realistic expectation of a non-spherical envelope shape.

Methods. Spherical harmonics are used to describe both the light source anisotropy and the envelope density distribution functions of the scattering particles. This framework demonstrates how the net resultant polarization arises from a superposition of three basic …

Discovery Of X-Ray Emission From The Wolf-Rayet Star Wr 142 Of Oxygen Subtype., L. M. Oskinova, W.-R. Hamann, A. Feldmeier, R. Ignace, Y.-H. Chu

Richard Ignace

We report the discovery of weak yet hard X-ray emission from the Wolf-Rayet (WR) star WR 142 with the XMM-Newton X-ray telescope. Being of spectral subtype WO2, WR 142 is a massive star in a very advanced evolutionary stage shortly before its explosion as a supernova or gamma-ray burst. This is the first detection of X-ray emission from a WO-type star. We rule out any serendipitous X-ray sources within approximate to 1 '' of WR 142. WR 142 has an X-ray luminosity of L(X) approximate to 7 x 10(30) erg s(-1), which constitutes only less than or similar to 10(-8) …

Spectropolarimetric Variability And Co-Rotating Structure In Hd 92207., Richard Ignace, S. Hubrig, M. Schöller

Richard Ignace

We report on low resolution (R~3000) spectropolarimetry of the A0 supergiant star HD 92207. This star is well-known for significant spectral variability. The source was observed on seven different nights spanning approximately 3 months in time. With a rotation period of approximately 1 year, our data covers approximately a quarter of the star's rotational phase. Variability in the continuum polarization level is observed over this period of time. The polarization across the Halpha line on any given night is typically different from the degree and position angle of the polarization in the continuum. Interestingly, Hbeta is not in emission and …

Elliptical Orbit Node Passage Time, Eric Addison

Eric Addison

The node passage time is calculated in order to gain an understanding of the kind of velocities and time scales will be involved in BEMRI simulations during close encounters with the SMBH. The result is generalized to produce a function of time with respect to theta, t(θ).

Modeling Forbidden Line Emission Profiles From Colliding Wind Binaries., R. Ignace, R. Bessey, C. S. Price

Richard Ignace

This paper presents calculations for forbidden emission-line profile shapes arising from colliding wind binaries. The main application is for systems involving a Wolf–Rayet (WR) star and an OB star companion. The WR wind is assumed to dominate the forbidden line emission. The colliding wind interaction is treated as an Archimedean spiral with an inner boundary. Under the assumptions of the model, the major findings are as follows. (i) The redistribution of the WR wind as a result of the wind collision is not flux conservative but typically produces an excess of line emission; however, this excess is modest at around …