Bulletin of the American Physical Society
71st Annual Gaseous Electronics Conference
Volume 63, Number 10
Monday–Friday, November 5–9, 2018; Portland, Oregon
Session NR1: Dissociative Electron Attachment and Related Phenomena |
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Chair: Samantha Fonseca, Rollins College Room: Oregon Convention Center A103-A104 |
Thursday, November 8, 2018 8:00AM - 8:30AM |
NR1.00001: Dissociative Electron Attachment to Gas-Phase Molecules. Invited Speaker: Sylwia Ptasinska Recently, we designed and developed an experimental technique to identify neutral radicals formed from decomposition following the dissociative electron attachment to gas phase molecules [1]. This process plays a significant role in nature and technology and has attracted a large amount of scientific attention in recent decades. Although numerous research groups around the world have probed the effects of low energy electrons on molecular fragmentation in the past, to date, due to experimental limitations, there has been no direct detection of the accompanying neutral radical species. To overcome this challenge, we initiated experiments using our newly developed stepwise electron spectroscopy to reveal a comprehensive picture of the dissociation process. We initially tackled a model molecule, carbon tetrachloride, but will continue on to a wide range of key molecular compounds. The detection of neutral radicals is essential for developing a thorough understanding of many research topics ranging from the elucidation of mechanisms in DNA damage (e.g., radiation damage to living organisms) [2] to improvements in high-resolution nanolithography (e.g., development of industrial applications). [1] Z. Li, A.R. Milosavljevic, I. Carmichael, S. Ptasinska, ``Direct Observation and Characterization of Neutral Radicals from a Dissociative Electron Attachment Process'' Phys. Rev. Lett. 119 (2017) 053402 [2] J.D. Gorfinkiel, S. Ptasinska "Electron scattering from molecules and molecular aggregates of biological relevance" J. Phys. B 50 (2017) 182001 [Preview Abstract] |
Thursday, November 8, 2018 8:30AM - 8:45AM |
NR1.00002: Investigation of difference between the rotational temperatures of ground and excited electronic states in a recombining nitrogen plasma at atmospheric pressure Augustin Tibere-Inglesse, Sean McGuire, Christophe Laux We report on a fundamental study of a recombining nitrogen plasma at atmospheric pressure, evidencing strong differences between the rotational temperatures of the ground and excited electronic states. The experiments were conducted using the CentraleSup\'{e}lec 50-kW plasma torch to provide an equilibrium nitrogen plasma at about 7000 K and 1 atm. The plasma was then forced to recombine rapidly by flowing through a water-cooled tube. At the exit of the tube, we performed Raman and Optical Emission Spectroscopy measurements of the ground and excited electronic states of N$_{\mathrm{2}}$. The rotational temperature of N$_{\mathrm{2}}$(X), is found to be 3200 K. The rotational temperature of N$_{\mathrm{2}}$(C) agrees with this temperature. In contrast, the rotational temperature of N$_{\mathrm{2}}^{\mathrm{+}}$(B) is higher, at 4600 K. The density of ground state atomic nitrogen was also indirectly measured and found to be nearly frozen in the tube. Therefore, it is strongly overpopulated with respect to its density at 3200 K at the exit of the tube. A clear relation is established between the overpopulation of atomic nitrogen and the difference between the rotational temperatures of N$_{\mathrm{2}}$(X) and N$_{\mathrm{2}}^{\mathrm{+}}$(B). Comparisons with CFD code show that the simulations are unable to predict the measured temperature decrease in this nonequilibrium situation. [Preview Abstract] |
Thursday, November 8, 2018 8:45AM - 9:00AM |
NR1.00003: First-Principles Molecular Spectra of Air Jeffery Leiding, Mark Zammit Comprehensive and high-accuracy experimental spectroscopy data for the rovibronic states of air molecules are critical to modeling of air in extreme conditions. However, with the lack of experimental data, first-principles approaches are key to generating complete molecular line lists. Here, we will discuss the methodology employed for the accurate calculation of molecular rovibronic states, and present opacity and equation of state results for nitric oxide (NO), which forms in significant abundance in air under extreme conditions. [Preview Abstract] |
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