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 Title: Short-lived Electronically-excited Diatomic Molecules Cooled Via Supersonic Expansion From A Plasma Microjet Author(s): Houlahan, Thomas J., Jr. Contributor(s): Eden, Gary; Su, Rui Subject(s): Mini-symposium: Spectroscopy in Kinetics and Dynamics Abstract: Using a pulsed plasma microjet to generate short-lived, electronically-excited diatomic molecules, and subsequently ejecting them into vacuum to cool via supersonic expansion, we are able to monitor the cooling of molecules having radiative lifetimes as low as 16 ns. Specifically, we report on the rotational cooling of He$_2$ molecules in the $d^3\Sigma_u^+$, $e^3\Pi_g$, and $f^3\Sigma_u^+$ states, which have lifetimes of 25 ns, 67 ns, and 16 ns, respectively. The plasma microjet is driven with a 2.6 kV, 140 ns high-voltage pulse (risetime of 20 ns) which, when combined with a high-speed optical imaging system, allows the nonequilibrium rotational distribution for these molecular states to be monitored as they cool from ~1200 K to below 250 K with spatial and temporal resolutions of below 10 $\mu$m and 10 ns, respectively. The spatial and temporal resolution afforded by this system also allows the observation of excitation transfer between the $f^3\Sigma_u^+$ state and the lower lying $d^3\Sigma_u^+$ and $e^3\Pi_g$ states. The extension of this method to other electronically excited diatomics with excitation energies $>$5 eV will also be discussed. Issue Date: 2014-06-16 Publisher: International Symposium on Molecular Spectroscopy Citation Info: Houlahan, J.; Eden, G.; Su, R. SHORT-LIVED ELECTRONICALLY-EXCITED DIATOMIC MOLECULES COOLED VIA SUPERSONIC EXPANSION FROM A PLASMA MICROJET. Proceedings of the International Symposium on Molecular Spectroscopy, Urbana, IL, June 16-21, 2014. DOI: 10.15278/isms.2014.MH13 Genre: CONFERENCE PAPER/PRESENTATION Type: Text Language: English URI: http://hdl.handle.net/2142/50818 DOI: https://doi.org/10.15278/isms.2014.MH13 Rights Information: Copyright 2014 by the authors. Licensed under a Creative Commons Attribution 4.0 International License. http://creativecommons.org/licenses/by/4.0/ Date Available in IDEALS: 2014-09-172015-04-14
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