A Caltech Library Service

Initial ionization rates in shock-heated Argon, Krypton, and Xenon

Harwell, Kenneth E. and Jahn, Robert G. (1964) Initial ionization rates in shock-heated Argon, Krypton, and Xenon. Physics of Fluids, 7 (2). pp. 214-222. ISSN 1070-6631. doi:10.1063/1.1711135.

[img] PDF - Published Version
See Usage Policy.

[img] PDF - Erratum
See Usage Policy.


Use this Persistent URL to link to this item:


The rate of ionization behind strong shock waves in argon, krypton, and xenon, is 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 2-in. sq. aluminum shock tube into ambient gases at pressures of 3.0 to 17.0 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 Gc/sec (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 ± 0.5 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 states of which the excitation step is rate controlling.

Item Type:Article
Related URLs:
Additional Information:© 1964 American Institute of Physics. Received 18 August 1963; revised manuscript received 11 September 1963. Online Publication Date: 9 December 2004. The research described in this paper was supported by the Daniel and Florence Guggenheim Jet Propulsion Center of the California Institute of Technology, and by the U. S. Air Force Office of Scientific Research. The authors wish to thank Professor F. E. Marble for his many contributions to the design and interpretation of these experiments. Mr. A. J. Kelly assisted with the construction and operation of the equipment, and Mr. H. Wong performed a series of related preliminary studies. Mrs. B. McAllister carried out many of the numerical computations.
Group:Guggenheim Jet Propulsion Center
Funding AgencyGrant Number
Daniel and Florence Guggenheim Jet Propulsion CenterUNSPECIFIED
Air Force Office of Scientific Research (AFOSR)UNSPECIFIED
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Guggenheim Jet Propulsion CenterUNSPECIFIED
Issue or Number:2
Record Number:CaltechAUTHORS:20110104-121347304
Persistent URL:
Official Citation:Initial Ionization Rates in Shock‐Heated Argon, Krypton, and Xenon Kenneth E. Harwell and Robert G. Jahn Phys. Fluids 7, 214 (1964); doi:10.1063/1.1711135 (9 pages)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:21581
Deposited By: Ruth Sustaita
Deposited On:04 Jan 2011 22:10
Last Modified:09 Nov 2021 15:58

Repository Staff Only: item control page