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 Title: TIME-RESOLVED POPULATIONS OF N2(A3Σu+,v) IN NANOSECOND PULSE DISCHARGE PLASMAS Author(s): Jans, Elijah R Contributor(s): Adamovich, Igor V.; Miller, Terry A.; Frederickson, Kraig Subject(s): Spectroscopy as an analytical tool Abstract: Absolute time-resolved populations of N$_{2}$(A$^{3}$$\Sigma$$_{u}$$^{+}) excited electronic state generated in a repetitive ns pulse discharge in nitrogen have been measured by Cavity Ring Down Spectroscopy (CRDS) and Tunable Diode Laser Spectroscopy (TDLAS). CRDS measurements of N_{2}(A^{3}$$\Sigma$$_{u}$$^{+}$,v=0-2) populations are made in the discharge afterglow at a pressures of 10-40 Torr. The data reduction procedure takes into account the linewidth of the pulsed laser source, comparable with the absorption linewidth and resulting in a non-single exponential ring down decay. Peak N$_{2}$(A$^{3}$$\Sigma$$_{u}$$^{+},v=0,1) populations after a 10-pulse ns discharge burst are 1.5x10^{11} cm^{-3}. In the afterglow, these populations exhibit a relatively slow decay with the characteristic time of approximately 500 \mus, most likely due to the quenching by the N2 molecules in the ground electronic state. TDLAS data have been taken at a higher pressure of 130 Torr. Absolute time-resolved N_{2}(A^{3}$$\Sigma$$_{u}$$^{+}$,v=0,1) number densities are measured during ns pulse discharge bursts up to 25 pulses long and in the afterglow, peaking at 5x10$^{12}$ cm$^{-3}$ and 3x10$^{13}$ cm$^{-3}$. The results indicate that N$_{2}$(A$^{3}$$\Sigma$$_{u}$$^{+}) is generated after every discharge pulse on a 20-50 \mus time scale, much longer compared to the discharge pulse duration, and decays between the pulses. The decay rate increases during the discharge burst. In the afterglow, N_{2}(A^{3}$$\Sigma$$_{u}$$^{+}$,v=0,1) populations decay significantly more rapidly compared to the low-pressure CRDS conditions, with the characteristic time of approximately 100 $\mu$s. The results demonstrate that both CRDS and TDLAS diagnostics can be used for time-resolved, absolute N$_{2}$(A$^{3}$$\Sigma$$_{u}$$^{+}) measurements in transient nonequilibrium plasmas and the afterglow, with the detection limit of \approx 10^{10} cm^{-3}. The data obtained using these two diagnostics are complementary, since TDLAS measurements can be used at the conditions when the N_{2}(A^{3}$$\Sigma$$_{u}$$^{+}$) populations may be too high, or vary too rapidly for accurate CRDS measurements. Issue Date: 2019-06-18 Publisher: International Symposium on Molecular Spectroscopy Genre: Conference Paper / Presentation Type: Text Language: English URI: http://hdl.handle.net/2142/104562 DOI: 10.15278/isms.2019.TL08 Rights Information: Copyright 2019 Elijah R Jans Date Available in IDEALS: 2019-07-152020-01-25
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