Physics Commons^™

Measurements Of Electron Density, Temperature And Photoionization Cross Sections Of The Excited States Of Neon In A Discharge Plasma, Shaukat Mahmood, Nek Shaikh, M. Kalyar, Naveed Piracha, M. Baig

Naveed K. Piracha

In the present work emission and absorption spectroscopy have been used to determine the plasma parameters of neon in a hollow cathode discharge lamp. The excitation temperature is determined using the intensity ratio method and Boltzmann’s plot method whereas the electron density is determined from the Stark broadening of the spectral lines. The behavior of the optogalvanic signal as a function of laser energy has been studied for three transitions from the 2p53s [1/2]2 metastable state following ΔJ=ΔK=0, ±1 dipole selection rules. The saturation technique has been used to measure the photoionization cross section from three intermediate states 2p53p′ [1/2]1, …

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.

The Study Of The 1s4–2pj Optogalvanic Transients In A Neon Discharge Plasma, Naveed Piracha, R. Feaver, T. Gilani, Rizwan Ahmed, R. Ali, M. Baig

Naveed K. Piracha

Time dependent optogalvanic signals induced by the 1s4→2pj laser excitations have been studied in neon DC plasma. The decay rates related to all the four 1si levels have been derived by fitting the waveforms with a mathematical rate equation model. The temporal signatures of three transitions namely 638.3, 650.7 and 724.5nm related to the 2p7, 2p8 and 2p10 upper levels, respectively, have been found to be different from the rest of the transitions. We relate these effects to the population redistribution of decaying channels and to the processes responsible for the optogalvanic effect.

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 …

Simulation Of Ultrashort Laser Pulse Propagation And Plasma Generation In Nonlinear Media. Dissertation, Jeremy Gulley

Jeremy R. Gulley

In this dissertation, a modified nonlinear Schrödinger equation is derived, which describes the propagation of ultrashort laser pulses through nonlinear materials in which plasma generation and laser-induced damage can occur. Differences between this model and models currently used in the literature are investigated and analyzed by numerical simulations. Ultrafast laser-induced material modification is investigated using this method by simulating the propagation of fully 3+1D (3 spatial plus 1 time dimension) laser pulses, which are numerically constructed from experimentally measured beam profiles and pulse shape data. The latest of these investigations reveals that standard rate-equation models for the free-electron plasma generation …

First Measurement Of The Neutron Beta Asymmetry With Ultracold Neutrons, Robert W. Pattie, J. Anaya, Henning O. Back, J. G. Boissevain, Thomas J. Bowles, Leah J. Broussard, Richard Carr, D. J. Clark, Scott Currie, S. Du, Bradley W. Filippone, Peter Geltenbort, A. García, Ayman I. Hawari, Kevin P. Hickerson, R. Hill, M. Hino, S. A. Hoedl, Gary E. Hogan, Anthony T. Holley, Takeyasu M. Ito, T. Kawai, K. Kirch, S. Kitagaki, Steve K. Lamoreaux, Chenyu Liu, Jingyang Liu, Mark Makela, Russell R. Mammei, J. W. Martin, Daniel Melconian, N. Meier, Michael P. Mendenhall, Charles L. Morris, R. Mortensen, A. Pichlmaier, Margaret L. Pitt, Blakely Plaster, John C. Ramsey, Roger Rios, Konstantin Sabourov, A. L. Sallaska, Alexander Saunders, R. Schmid, Susan J. Seestrom, C. Servicky, Sky K. L. Sjue, D. Smith, Walter E. Sondheim, E. Tatar, W. Teasdale, Christopher R. Terai, B. Tipton, M. Utsuro, R. Bruce Vogelaar, Bernard Wehring, Y. P. Xu, Andrew R. Young, J. Yuan

Robert W. Pattie Jr.