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Title:Supersonic cooling of short-lived molecular states in a pulsed microcavity plasma jet
Author(s):Su, Rui
Department / Program:Electrical & Computer Eng
Discipline:Electrical & Computer Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:M.S.
Genre:Thesis
Subject(s):microplasma
supersonic cooling
molecular spectroscopy
Abstract:Electronic states of helium diners having potential energy > 24 eV and radiative lifetimes as short as 19 ns have been generated in a micro-plasma jet at super-atmospheric pressure and rotationally cooled by supersonic expansion. Spatial-temporal spectrograms of d^3Σ+u→(b^3)π_g (v', v") = (0, 0) emission are obtained, which contain the information about the dynamic cooling process during the molecular beam expansion. Analysis shows the spatial-temporal evolution of the rotational temperature to be a damped sinusoid that reaches a minimum value of 100 K, which is attributed to the reflection of electrons from a virtual cathode located downstream of the jet nozzle. Data fitting to the damped sinusoid function yields a spatially-averaged electron density of 10^8 cm^(-3). The experimental setup has the potential to be used in exploration of the spectroscopy and plasma dynamics in various gas molecules.
Issue Date:2016-04-05
Type:Thesis
URI:http://hdl.handle.net/2142/90736
Rights Information:Copyright 2016 Rui Su
Date Available in IDEALS:2016-07-07
Date Deposited:2016-05


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