2026-09-21T03:20:36Z https://www.ideals.illinois.edu/oai-pmh

oai:www.ideals.illinois.edu:2142/24061 2023-07-10 col_2142_8859 col_2142_5131 com_2142_8858 com_2142_234 com_2142_5130

Eden, James G. Cooper, S. Lance Eden, James G. Hertzog, David W. Carney, Paul S. Keister, Kathryn E. 2011-05-25T14:53:01Z 2011-05-25T14:53:01Z 2011-05-25T14:53:01Z 2011-05 Measurements of the temporal decay of the absolute electron density in a laser-produced plasma channel have been made with a 9.2~Ghz microwave interferometer. The plasma channels were generated by sub-picosecond laser pulses ($\lambda=$248~nm, 40~mJ per pulse) produced by a hybrid Ti:sapphire/KrF excimer amplifier system. The ultrashort pulse duration resulted in a $\delta$-function excitation source, allowing the subsequent plasma decay to be explored without further excitation of the gas and without deconvolving the excitation source profile from the electron density decay data. The temporal resolution of the interferometer has been demonstrated to be a few nanoseconds (bandwidth of $\approx$1~GHz), and electron density decay profiles have been measured in argon and nitrogen at pressures in the range of 1-650~Torr. Gas kinetic models in argon and nitrogen have been developed, and have shown good agreement with the measured electron density profiles. Model predictions of the dissociative recombination rate constants, $\alpha_D$, in argon and nitrogen are reported, \mbox{$\alpha_D\,(\mathrm{Ar})=1-6 \times 10^{-6}$~cm$^3$~s$^{-1}$} and \mbox{$\alpha_D\,(\mathrm{N}_2)=1-3.25 \times 10^{-6}$~cm$^3$~s$^{-1}$}. At pressures $>$200~Torr, the reported values show good agreement with previous measurements, and in the pressure range 20-200~Torr, the values presented here are the first to be reported. The multiphoton ionization (MPI) cross section for argon, $\sigma_{(4)}$, is estimated to be in the range $10^{-117}-10^{-118}$~cm$^8$~s$^3$, which is within an order of magnitude of the one previous measurement, and the experimental technique is shown to have the potential to improve the precision of this estimate. Item withdrawn by Mark Zulauf (zulauf@illinois.edu) on 2010-12-03T20:28:19Z Item was in collections: University of Illinois Theses & Dissertations (ID: 1) No. of bitstreams: 1 Keister_Kathryn.pdf: 25872508 bytes, checksum: 425f2099c3b22818d091314b9c287887 (MD5) Made available in DSpace on 2011-05-25T14:53:01Z (GMT). No. of bitstreams: 2 Keister_Kathryn.pdf: 25872508 bytes, checksum: 425f2099c3b22818d091314b9c287887 (MD5) license.txt: 4065 bytes, checksum: 8722e8e2f21bff629710d9f7c61cde1c (MD5) http://hdl.handle.net/2142/24061 en Copyright 2011 Kathryn E. Keister plasma microwave argon nitrogen dissociative recombination multiphoton ionization electron density plasma filaments Microwave Interferometric Measurements of Electron Density in Laser-Generated Plasma Channels Physics 1244 Physics 0240 University of Illinois at Urbana-Champaign Dissertation Ph.D. PHD:Physics -UIUC 10KS0240PHD