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<p class="MsoNormal">Please join us Friday January 18, 2019 for Dr. Igor Adamovich’s seminar on
<i>“Laser Diagnostics for Measurements of Electric Field and Excited Metastable Species in Nonequilibrium Plasmas and Reacting Flows.”
</i>The seminar will be held in 4138 Physics Research Building at 12:30pm, light refreshments will be provided shortly before the seminar. More information on Dr. Adamovich’s talk is below:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Abstract: <o:p></o:p></p>
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<span style="font-size:10.5pt;font-family:"Arial",sans-serif;color:#222222">Non-intrusive laser diagnostic measurements of temporal and spatial distributions of electric field and the number densities of excited metastable species in nonequilibrium plasmas
are essential for development of engineering applications such as plasma flow control, plasma-assisted combustion, plasma materials processing, and plasma medicine. This talk presents an overview of recent electric field and species measurements in ns pulse
discharge plasmas, by ps Four-Wave Mixing (FWM), ps Electric Field Induced Second Harmonic (EFISH) generation, Cavity Ring Down Spectroscopy (CRDS), and Tunable Diode Laser Absorption Spectroscopy(TDLAS) .<o:p></o:p></span></p>
<p class="MsoNormal" style="background:white;vertical-align:baseline"><span style="font-size:10.5pt;font-family:"Arial",sans-serif;color:black">Picosecond FWM measurements have been done in ns pulse discharges in ambient air, for several electrode geometries.
For short voltage rise times of several ns, peak electric field considerably exceed the DC breakdown threshold. Sub-nanosecond time resolution is obtained by monitoring the timing of individual laser shots relative to the voltage pulse, and post-processing
four-wave mixing signals saved for each laser shot, placing them in the appropriate “time bins”. The main advantage of EFISH over FWM is that it is considerably more sensitive and species independent, such that it can be used in any high-pressure plasma. Ps
EFISH is used to measure electric field in dielectric barrier discharge plasma flow actuators, atmospheric pressure flames enhanced by transient plasmas, and atmospheric pressure plasma jets. In both techniques, electric field vector components are isolated
by monitoring signals with different polarizations, and absolute calibration is done by measuring a known Laplacian field.<o:p></o:p></span></p>
<p class="MsoNormal" style="background:white;vertical-align:baseline"><span style="font-size:10.5pt;font-family:"Arial",sans-serif;color:black"> <o:p></o:p></span></p>
<p class="MsoNormal" style="background:white;vertical-align:baseline"><span style="font-size:10.5pt;font-family:"Arial",sans-serif;color:black">Absolute time-resolved populations of N2(A3Óu+) excited electronic state, which is a major precursor of O atoms and
NO in air plasmas, as well as H atoms and other radical species in fuel-air plasmas, are measured in a repetitive ns pulse discharge and the afterglow in nitrogen. Two complementary techniques are used, CRDS (at a relatively low pressure of 11 Torr) and single-pass
TDLAS (at an intermediate pressure of 130 Torr). In the afterglow of a low-pressure discharge, N2(A3Óu+,v=0-2) populations exhibit a relatively slow decay on the time scale of about 500 ìs. In a medium pressure discharge, N2(A3Óu+,v=0,1) populations decay
significantly more rapidly compared to the low-pressure conditions, both between the discharge pulses and in the afterglow, on the time scale of 50-100 ìs. In both cases, the decay is likely due to the quenching by the vibrationally excited N2 molecules in
the ground electronic state.<o:p></o:p></span></p>
<p class="MsoNormal" style="background:white;vertical-align:baseline"><span style="font-size:10.5pt;font-family:"Arial",sans-serif;color:black"> <o:p></o:p></span></p>
<p class="MsoNormal" style="background:white;vertical-align:baseline"><span style="font-size:10.5pt;font-family:"Arial",sans-serif;color:black">The results demonstrate considerable potential of laser diagnostic techniques for characterization of high-pressure
nonequilibrium plasmas, where they provide quantitative insight into kinetics of ionization, charge transport, molecular energy transfer, energy thermalization rate, and plasma chemical reactions.<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><img width="224" height="45" style="width:2.3333in;height:.4687in" id="Picture_x0020_1" src="cid:image001.png@01D4A9A0.2346C8D0" alt="The Ohio State University"><span style="font-size:9.0pt;font-family:"Arial",sans-serif;color:#333333"><br>
</span><b><span style="font-size:9.0pt;font-family:"Arial",sans-serif;color:#BB0000;background:white">Kyle Schechter</span></b><span style="font-size:9.0pt;font-family:"Arial",sans-serif;color:#333333">, Fiscal</span><span style="font-size:9.0pt;font-family:"Helvetica",sans-serif;color:#333333">
Associate<br>
</span><span style="font-size:9.0pt;font-family:"Helvetica",sans-serif;color:#BB0000;background:white">Department of Physics</span><span style="font-size:9.0pt;font-family:"Helvetica",sans-serif;color:#333333"><br>
4112 Physics Research Building | 191 West Woodruff Avenue Columbus, OH 43210<br>
614-292-7260 Office <br>
</span><b><span style="font-size:9.0pt;font-family:"Helvetica",sans-serif;color:blue;background:white"><a href="mailto:Schechter.19@osu.edu"><span style="color:blue">Schechter.19@osu.edu</span></a></span></b><b><span style="font-size:9.0pt;font-family:"Helvetica",sans-serif;color:#333333;background:white">
</span></b><span style="font-size:9.0pt;font-family:"Helvetica",sans-serif;color:#333333"><a href="http://osu.edu/" target="_blank"><b><span style="color:blue;background:white">osu.edu</span></b></a></span><o:p></o:p></p>
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