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Title: | Pulsed plasma microjets: a new tool for the investigation of plasma kinetics and molecular spectroscopy |
Author(s): | Houlahan, Thomas |
Director of Research: | Eden, James G. |
Doctoral Committee Chair(s): | Eden, James G. |
Doctoral Committee Member(s): | Carney, Paul S.; Cunningham, Brian T.; Gruebele, Martin; McCall, Benjamin J. |
Department / Program: | Electrical & Computer Eng |
Discipline: | Electrical & Computer Engr |
Degree Granting Institution: | University of Illinois at Urbana-Champaign |
Degree: | Ph.D. |
Genre: | Dissertation |
Subject(s): | supersonic cooling
plasma jet short-lived molecular states |
Abstract: | We report on the development of a new laboratory tool which is suitable both for generating and quickly cooling short-lived molecules, and also for studying the kinetics and dynamics that take place at the rotational level during the expansion process. By integrating a microplasma device with a supersonic nozzle, temperatures as low as 50 K were achieved for molecules having lifetimes shorter than 40 ns and excitation (internal) energies ≳ 11 eV. Additionally, final temperatures ranging from 90 K to 900 K for a set of nested electronic states were observed in the He2 excimer, and a highly non-equilibrium rotational distribution was recorded for the lowest of these nested states. This rotational distribution was analyzed with a kinetic mode and shown to be due primarily to collisional excitation transfer and rotational relaxation. Since collisions are the means by which the supersonic expansion process cools atoms/molecules, this result perhaps demonstrates a fundamental restriction on which molecular states can and cannot be effectively cooled in a supersonic expansion. The rate constant for rotational relaxation within the He2(d3Σu+) state was determined to be (9.4 ± 0.1) × 10-13 cm3s-1, while the rate constant for collisional excitation transfer between rotational levels of the He2(e3Πg) and He2(d3Σu+) states was found to scale as (9.8 ± 5.9 × 10-14 cm3s-1)exp(-(6.4 × 10-3)/ ΔE*B). |
Issue Date: | 2015-01-21 |
URI: | http://hdl.handle.net/2142/72742 |
Rights Information: | Copyright 2014 Thomas J. Houlahan, Jr. |
Date Available in IDEALS: | 2015-01-21 |
Date Deposited: | 2014-12 |
This item appears in the following Collection(s)
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Dissertations and Theses - Electrical and Computer Engineering
Dissertations and Theses in Electrical and Computer Engineering -
Graduate Dissertations and Theses at Illinois
Graduate Theses and Dissertations at Illinois