Bulletin of the American Physical Society
2013 Joint Meeting of the APS Division of Atomic, Molecular & Optical Physics and the CAP Division of Atomic, Molecular & Optical Physics, Canada
Volume 58, Number 6
Monday–Friday, June 3–7, 2013; Quebec City, Canada
Session J5: Invited Session: AMO Applications in Gaseous Electronics |
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Chair: Tim Gay, University of Nebraska Room: 301 |
Wednesday, June 5, 2013 2:00PM - 2:30PM |
J5.00001: Computational Methods for Electron-Atom Collisions in Plasma Applications Invited Speaker: Klaus Bartschat |
Wednesday, June 5, 2013 2:30PM - 3:00PM |
J5.00002: Control of ion energy distributions on plasma electrodes Invited Speaker: Demetre Economou Control of the energy of ions bombarding a substrate is important for both plasma etching and deposition. As device dimensions keep shrinking, requirements on selectivity and substrate damage become ever more stringent. Such requirements impose strict limits not only on the mean ion energy, but also of the ion energy distribution (IED). Methods to control the IED will be presented and discussed from both experimental and simulation points of view. Such methods include (a) application of tailored voltage waveforms on the substrate electrode in \textit{continuous wave plasmas}, and (b) application of synchronous bias on a ``boundary electrode'' during a specified time window in the afterglow of \textit{pulsed plasmas}. Simulations employing the PIC-MCC method, and a rapid simulation based on an equivalent circuit model will be presented and tested against experimental observations. The ``inverse problem'', i.e., that of determining the voltage waveform that yields a desired IED, will also be discussed. [Preview Abstract] |
Wednesday, June 5, 2013 3:00PM - 3:30PM |
J5.00003: EBIT measurements of excitation and ionization by electron impact Invited Speaker: Hui Chen Electron-impact excitation and electron-impact ionization are fundamental atomic processes that are critical for describing both the ionization balance and the radiative emission of ions in plasmas. The properties of the electron beam ion trap (EBIT) made it a highly useful device for measuring electron-impact cross sections of highly charged ions. Moreover, the recent development and use of x-ray microcalorimeter array detectors made it possible to extend cross section determinations to ions with multiple valence electrons and to measure the ionization equilibrium of complex ions. Since EBIT's inception in the 1980's measurements include cross sections of direct and indirect (resonance) excitation as well as cross sections of single-electron ionization of K-shell and L-shell ions of Ti, V, Cr, Mn, and Fe. Studies of very high-Z elements, such as Xe, Au and U, have been performed, showing the importance of the Breit interaction, which in the case of K-shell uranium ions increases the ionization cross section by 50{\%}. This talk will review the results of such measurements performed at EBIT for nearly three decades.~ [Preview Abstract] |
Wednesday, June 5, 2013 3:30PM - 4:00PM |
J5.00004: On the role of electron-driven processes in planetary and cometary atmospheres Invited Speaker: Laurence Campbell Electrons in the solar wind and photoelectrons produced by sunlight, sometimes accelerated in the magnetosphere, produce ionisation, dissociation and excitation of atoms and molecules in planetary and cometary atmospheres. These primary electrons, and secondary electrons from ionisation, interact further, progressively losing energy until reaching thermal equilibrium. The product ions and excited species take part in chemical reactions, producing new species. Thus electron-driven processes are significant in determining the populations of minor species and the rates of energy transfer in upper-planetary and cometary atmospheres. The radiation emitted by excited species is valuable in remote sensing. Thus modelling of electron-driven processes is necessary in both observing and understanding these atmospheres. This requires detailed simulation of a large number of electron-impact processes and subsequent radiative and collisional processes, including chemical reactions, which have a vast range of time scales from nanoseconds to days. In most cases thermal equilibrium is not attained, so a statistical-equilibrium calculation is employed. Some vibrational excitations and the products of many slower reactions do not reach statistical equilibrium, hence non-equilibrium calculations are also required. In all such calculations the availability of accurate atomic and molecular data, such as electron-impact cross sections, is critical. Here we show the parallel application of new electron-impact excitation cross sections and enhanced computational techniques in a number of examples, including the determination of the abundance of carbon monoxide in comet Hale-Bopp, electron heating rates in the atmosphere of Titan, predictions of infrared emissions from the upper atmospheres of Mars and Venus and non-equilibrium processes in the atmosphere of Jupiter. [Preview Abstract] |
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