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 Title: Cooling of electronically-excited He2 molecules in a microcavity plasma jet Author(s): Su, Rui Contributor(s): Eden, J. Gary; Houlahan, Thomas J., Jr. Subject(s): Dynamics and kinetics Abstract: Helium dimers in the d$^{3}\Sigma^{+}_{u}$ excited electronic state with potential energy $>$24 eV and radiative lifetime of 25 ns have been generated in a microcavity plasma jet and rotationally cooled by supersonic expansion in vacuum. The dynamic process of cooling is recorded by imaging the axis of expansion onto the slit of Czerny-Turner spectrometer, yielding spatial-temporal spectrograms of d$^{3}\Sigma^{+}_{u}$$\rightarrow$$b^{3}\Pi_{g}$ $(v', v'')=(0, 0)$ emission. Analysis of the data shows the spatial-temporal evolution of the rotational temperature to be a damped sinusoid that reaches a minimum value of 100K. This reproducible behavior is attributed to the reflection of electrons from a virtual cathode located downstream of the nozzle and indicates that the spatially-averaged electron density is 10$^{8}$ cm$^{-3}$. We present this observed rotational temperature oscillation during the supersonic cooling process as an example of the potential of our supersonic microplasma expansion as a tool to explore physical dynamics in diatomic molecules having high excitation energies and small lifetimes. Issue Date: 2016-06-24 Publisher: International Symposium on Molecular Spectroscopy Genre: Conference Paper/Presentation Type: Text Language: En URI: http://hdl.handle.net/2142/91477 Rights Information: Copyright 2016 by the authors Date Available in IDEALS: 2016-08-22
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