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Emissivities and Absorptivities of Gases


Thomson, James Alex Lloyd (1958) Emissivities and Absorptivities of Gases. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/2HJG-SD13.


Equilibrium emissivities and absorptivities of heated gases have been computed from spectroscopic data. Several problems have been studied: (1) The relation between equilibrium absorptivities and equilibrium emissivities for diatomic and polyatomic molecules has been investigated. Our theoretical results provide a satisfactory correlation of available experimental data for heated water vapor but not for carbon dioxide. The origin of the failure of the theory for carbon dioxide is discussed in detail. (2) The available, empirically determined, emissivity data for water vapor have been correlated in terms of a statistical model for the distribution of spectral lines within well-defined wavelength regions corresponding to the stronger vibration-rotation bands. This correlation provides a useful framework for the extrapolation of measured emissivity data to temperatures and pressures somewhat different from those used to obtain the experimental data. (3) The equilibrium emissivity of heated NO has been calculated for the conditions under which this molecule exists in high-temperature air during reentry of hypersonic missiles. An extension of the Mayer-Goody statistical model was used for emissivity calculations on NO. Our semi-analytical results are in acceptable agreement with a simpler numerical analysis of Kivel, Mayer and Bethe. The original investigations of gas absorptivities and emissivities are introduced with a brief survey of basic theoretical results. An attempt has also been made to calculate the dipole moments and low energy transition probabilities for HF, HCl, and HBr. In this study it was found that the intensities of lines lying in the infrared are very sensitive to the details of the approximating wavefunctions. A considerably more detailed description of the wavefunctions than is available at present is required to make confident predictions of absolute intensities from first principles.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:(Engineering Science and Physics)
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Engineering
Minor Option:Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Penner, Stanford S.
Thesis Committee:
  • Unknown, Unknown
Defense Date:1 January 1958
Record Number:CaltechETD:etd-01232006-143205
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:292
Deposited By: Imported from ETD-db
Deposited On:24 Jan 2006
Last Modified:17 Oct 2023 16:35

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PDF (Thomson_ja_1958.pdf) - Final Version
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