The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform

Colm T Whelan - One of the best experts on this subject based on the ideXlab platform.

  • electron and positron impact ionization of Inert Gases
    Physical Review A, 2018
    Co-Authors: R I Campeanu, H R J Walters, Colm T Whelan
    Abstract:

    Triple-differential cross sections (TDCS) are presented for the electron and positron impact ionization of Inert gas atoms in a range of geometries where a number of significant few body effects compete to define the shape of the TDCS. Using both positrons and electrons as projectiles has opened up the possibility of performing complementary studies which could effectively isolate competing interactions which cannot be separately detected in an experiment with a single projectile. A comparison is presented between theory and the recent experiments of [Gavin, deLucio, and DuBois, Phys. Rev. A 95, 062703 (2017)] for ${e}^{\ifmmode\pm\else\textpm\fi{}}$ and contrasted with the results from earlier electron experiments. For the special case of xenon($5p$), cross sections are presented for both electron- and positron-impact ionization in kinematics where the electron case appears well understood. The kinematics are then varied in order to focus on the possible role of distortion, exchange, and target wave-function effects.

  • energy sharing e 2 e collisions ionization of the Inert Gases in the perpendicular plane
    Physical Review A, 2015
    Co-Authors: F K Miller, H R J Walters, Colm T Whelan
    Abstract:

    The triple differential cross section for ionization of the Inert Gases He, Ne, Ar, Kr, and Xe in energy-sharing perpendicular plane geometry is investigated. Encouraging agreement with recent experiments is found using the distorted-wave Born approximation (DWBA). Mechanisms are discussed which explain the He and Ne data but which seem to be masked by the greater distortion effects in the heavier targets. The inclusion of postcollisional interaction is explored using Gamow, ${N}_{ee}$, and Ward-Macek, ${M}_{ee}$, factors. While both help to improve the shape of the cross section for He and Ne at the lower energies, they are not successful for the other targets, and both factors prove to be too strong for all the Inert Gases with increasing impact energy. It is well known that ${N}_{ee}$ destroys normalization. Comparing DWBA $+\phantom{\rule{0.16em}{0ex}}{M}_{ee}$ results with some absolute experimental points at 1 and 2 eV indicates that it is also not to be trusted on normalization. An interesting situation with Ar is highlighted near 25 eV, where the cross section may be tending towards a strong interference minimum or zero.

Suguo Chen - One of the best experts on this subject based on the ideXlab platform.

I M Hutchings - One of the best experts on this subject based on the ideXlab platform.

  • influence of Inert Gases on ionized magnetron plasma deposition of carbon nitride thin films
    Surface & Coatings Technology, 2003
    Co-Authors: Yukihiro Kusano, Z H Barber, J E Evetts, I M Hutchings
    Abstract:

    Abstract Carbon nitride films were deposited by ionized magnetron sputtering in gas mixtures containing helium, neon, argon or krypton plus nitrogen. Sputtering voltages and deposition rates were measured, and the films were characterized by Fourier transform infrared (FTIR) spectroscopy, Rutherford back-scattering and nano-indentation. Application of an inductive plasma decreased the sputtering voltage, suggesting a decrease in the impedance of the discharge. A stable discharge was only obtained at pressures above 8 Pa in helium/nitrogen mixtures. The deposition rates increased with nitrogen content in neon, argon or krypton mixtures, both with and without an inductive plasma. The deposition rates with an inductive plasma in krypton/nitrogen were much higher than those in argon/nitrogen and neon/nitrogen mixtures with the same nitrogen contents. IR absorption bands at 1250, 1500 and 2200 cm−1 indicated the presence of disordered sp2 hybridized carbon, graphite-like sp2 carbon, and nitrile/isocyanate groups, respectively. In addition, amide-like vibration between 2800 and 3700 cm−1 was pronounced on application of the inductive plasma. FTIR results suggest that less dense films were synthesized with the inductive plasma. The N:C ratio was

Karoly Osvay - One of the best experts on this subject based on the ideXlab platform.

  • Measurement of pressure dependent nonlinear refractive index of Inert Gases
    Optics express, 2010
    Co-Authors: Adam Borzsonyi, Zsuzsanna Heiner, Attila Kovács, Mikhail Kalashnikov, Karoly Osvay
    Abstract:

    The propagation of high intensity laser beams is excessively affected by optical nonlinear effects, thereby the knowledge of the nonlinear refractive indices of the beam guiding media is indispensable in the design of laser systems and experiments. Apart from undesired self-focusing, several areas of modern laser spectroscopy can utilize optical nonlinearity, from LiDAR measurements to filamentation. In this paper we report on a direct measurement of pressure dependent nonlinear refractive index of Ar, N2, Ne, Xe, and air between 0.05 mbar and 1 bar, based on the powerful technique called spectrally and spatially resolved interferometry. In this way the total value of nonlinear refractive index is measured, that is the sum of all elementary phenomena contributing to the intensity dependent refractivity of the Gases.

  • dispersion measurement of Inert Gases and gas mixtures at 800 nm
    Applied Optics, 2008
    Co-Authors: Adam Borzsonyi, Zsuzsanna Heiner, Attila Kovács, Mikhail Kalashnikov, Karoly Osvay
    Abstract:

    Dispersion of femtosecond laser pulses propagating in Ar, He, Kr, N2, Ne, Xe, and their mixtures is measured by spectrally and spatially resolved interferometry. By varying the gas pressure in a 4.5 m long tube between 0.05 mbar and ambient pressure, the first, second, and third order phase derivatives of broadband laser pulses are determined at 800 nm under standard conditions. The dispersion of Gases and gas mixtures obeys the Lorentz-Lorenz formula with an accuracy of 0.7%. Based on the measured pressure dependent dispersion values in the near infrared and the refractive indices available from the literature for the ultraviolet and visible, a pressure dependent Sellmeier-type formula is fitted for each gas. These common form, two-term dispersion equations provide an accuracy between 4.1×10−9 (Ne) and 4.3×10−7 (Xe) for the refractive indices, from UV to near IR.

Jari Ihonen - One of the best experts on this subject based on the ideXlab platform.

  • optimization study of purge cycle in proton exchange membrane fuel cell system
    Journal of Power Sources, 2013
    Co-Authors: Kaj Nikiforow, Henri Karimaki, Tommi Keranen, Jari Ihonen
    Abstract:

    Abstract In PEMFC ( proton exchange membrane fuel cell ) systems operating in dead-end mode, hydrogen purges are needed to remove accumulated Inert Gases and liquid water from the anode side of the fuel cell stack. Hydrogen purges were studied using different humidity levels, purge times, and purge triggering criteria. The purged gas volume and composition were accurately measured with fast data acquisition and an advanced experimental set-up. The experiments were done with constant current density with aim of keeping the anode gas recirculation rate constant. Fuel utilization per pass varied as the hydrogen content on the anode side changed. This study demonstrates how the optimized purge strategy changes with a changing humidity level. It also shows that high fuel efficiency (>99%) is easily reached and that with optimized purge strategy a very high fuel efficiency (99.9%) can be reached. It was also shown that concentration polarization due to accumulation of Inert Gases on the anode side is two times higher than values obtained by theoretical calculations. This result is significant for purge strategy and system design.