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Initial Ionization Rates in Shock-Heated Argon, Krypton, and Xenon


Harwell, Kenneth Edwin (1963) Initial Ionization Rates in Shock-Heated Argon, Krypton, and Xenon. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/HW2S-MW55.


The rates of ionization behind strong shock waves in argon, krypton, and xenon are observed by a transverse microwave probe over a range of electron densities low enough that atom-atom inelastic collisions are the rate determining mechanism. Shocks of Mach number 7.0 to 10.0 propagate down a 5 cm square aluminum shock tube into ambient gases at pressures of 3 to 17 mm Hg, heating them abruptly to atomic temperatures of 5500°K to 9600°K. The subsequent relaxation toward ionization equilibrium is examined in its early stages by the reflection, transmission, and phase shifts of a 24.0 Kmc (1.25 cm) transverse microwave beam propagating between two rectangular horns abreast a glass test section. The data yield effective activation energies of 11.9 +/- 0.5 ev for argon, 10.4 +/- 0.5 ev for krypton, and 8.6 +/- 0.6 ev for xenon. These coincide, within experimental error, with the first excitation potentials, rather than the ionization potentials of the gases, indicating that in this range, ionization proceeds via a two-step process involving the first excited electronic state. Within experimental error, the pressure dependence is found to be proportional to the number density squared.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:(Aeronautics)
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Aeronautics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Jahn, Robert G.
Thesis Committee:
  • Unknown, Unknown
Defense Date:1 January 1963
Additional Information:Title varies in the 1963 Caltech commencement program: Initial Ionization of Shock-Heated Argon, Krypton, and Xenon
Record Number:CaltechETD:etd-12072005-144544
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:4838
Deposited By: Imported from ETD-db
Deposited On:08 Dec 2005
Last Modified:03 Jan 2024 00:35

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PDF (Harwell_ke_1963.pdf) - Final Version
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