Bulletin of the American Physical Society
62nd Annual Gaseous Electronics Conference
Volume 54, Number 12
Tuesday–Friday, October 20–23, 2009; Saratoga Springs, New York
Session LW2: Atomic Data for Modeling |
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Chair: Dmitry Fursa, Curtin University of Technology Room: Saratoga Hilton Ballroom 2 |
Wednesday, October 21, 2009 8:00AM - 8:30AM |
LW2.00001: Electron impact excitation data for modeling planetary atmospheres and cometary comae Invited Speaker: Measurements were undertaken of electron impact cross sections for vibrational and electronic excitation of NO. Incorporation of these in models showed that electron impact excitation produced a proportion of the (1$\to $0) emissions near 5.3 $\mu $m in aurora. A study of the role of electronically excited N$_{2}$ in the production of nitric oxide, using new compilations of the relevant cross sections, showed that electron-impact excitation is significant. A compilation of recent experimental and theoretical cross sections for electron impact excitation of vibrational modes in CO$_{2}$ was undertaken and applied in an updated calculation of electron cooling rates in the atmosphere of Mars. These rates were found to be substantially larger in the very cold part of the Martian upper atmosphere, giving a possible explanation for why that region was measured to be colder than expected from modeling. Recent theoretical cross sections for electron-impact excitation of the A $^{1}\Pi $ state of CO were shown to be consistent with recent laboratory measurements. They were then applied in a simulation of the Fourth Positive emissions from CO in comet Hale-Bopp. It was found that the electron-impact excitation component is substantial, with implications for one estimate of the abundance of CO in the comet. [Preview Abstract] |
Wednesday, October 21, 2009 8:30AM - 9:00AM |
LW2.00002: Electron-molecule processes relevant to planetary atmospheres Invited Speaker: Electron-molecule collisions play an important role in the nitrogen-rich upper atmospheres of Titan, Triton, and Earth. Modeling these processes requires accurate laboratory data. To this end, measurements and analyses of recent electron impact excitation experiments with molecular nitrogen are presented. Absolute excitation cross sections for transitions from the $X\,^1\Sigma_g^+$($v^{\prime\prime}$=0) to the $C\,^3\Pi_u$, $E\,^3\Sigma_g^+$, $a^{\prime\prime}\,^1\Sigma_g^+$, $b\,^1\Pi_u$, $c_3\,^1\Pi_u$, $o_3\,^1\Pi_u$, $b^{\prime}\,^1\Sigma_u^+$, $c_4^{\prime}\,^1\Sigma_u^+$, $G\,^3\Pi_u$ and $F\,^3\Pi_u$ states are determined from electron energy loss measurements, integrated over a broad range of scattering angles, with incident electron energies ranging from 13 eV to 100 eV. Vibrationally resolved excitation of the $C\,^3\Pi_u$($v^{\prime}$) state for the $v^{\prime}$=0, 1, 2, 3, and 4 levels will also be discussed, which indicates non-Franck-Condon behavior below roughly 30 eV. Results from rotationally resolved electron-impact induced VUV emission measurements will also be discussed. Of particular interest is the predicted variation of predissociation yield with increasing rotational quantum number. This is expected to introduce additional temperature dependencies to atmospheric models. Preliminary results of vibrationally resolved excitation functions for electron impact induced emissions of the Lyman-Birge-Hopfield (LBH) band system will be presented. Finally, we will discuss an investigation into e$-$H$_2$ processes related to the Jovian and Saturnian aurora as well as the recently identified atomic hydrogen plume on Saturn. [Preview Abstract] |
Wednesday, October 21, 2009 9:00AM - 9:30AM |
LW2.00003: Atomic Data Needs for Modeling Supernova Light Curves Invited Speaker: The modeling of supernovae requires the application of knowledge from a wide range of numerical and physical disciplines. The requisite expertise includes hydrodynamics, radiation transport, nuclear physics and atomic physics. Recently, there has been increased interest in improving the number and quality of supernova observations, as exemplified by missions such as NSF's Large Synoptic Survey Telescope (LSST) and NASA/DOE's Joint Dark Energy Mission (JDEM). In support of these missions, the corresponding modeling efforts are also being expanded. In this talk, the role of atomic data is discussed as it pertains to the modeling of radiation emitted by supernovae. The Los Alamos OPLIB opacity database has previously been used in this context to provide atomic opacities for modeling plasmas under local thermodynamic equilibrium (LTE) conditions. The Los Alamos suite of atomic physics codes is currently being used to explore options for providing non-LTE atomic physics data in order to model plasmas under more complicated conditions. [Preview Abstract] |
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