Publication Abstracts

Moore 1971

Moore, J.A., 1971: Infrared Absorption of Carbon Dioxide at High Densities with Application to the Atmosphere of Venus. Ph.D. thesis. Columbia University.

Several previously undiscovered infrared absorptions have been found with carbon dioxide. All are normally forbidden, and were collision-induced in an absorbing cell whose combination of pressure and path length has a unique sensitivity for induced absorptions.

The most throughly studied new absorptions, the 2.3μ region, were measure to 95 amagat over path lengths of 2400 cm. They are attributed to transitions from ground to the 311 Fermi pair at 4248 and 4391 cm-1. Total strength, including the associated hot bands, is (6.2±0.9)×10-6 cm-2ama-2. The strength ratio between the two members of the pair has been used to find the ratio of the unperturbed matrix elements: that of the 0000-1111 transition is 8 times larger than that of the 0000-0311, with a crossing-over of intensities between the unperturbed and perturbed states.

Other newly-observed induced absorption are attributed to simultaneous CO2-N2 transitions, and to the 0000-0002 transition in CO2. In addition, measurements were made for the first time of induced absorptivities in spectral "windows" — regions usually considered transparent — at 11.2, 10.0, and 8.75μ, and of the induced strength of 0000-0111 transition.

The absorption strengths measures in this study are combined with others from previously published work to obtain a number of CO2 polarizability derivatives, and to exhibit regular progressions in strengths versus increasing ν2 quantum number, for both allowed and induced transitions.

Absorptivities in the windows were used to test and reject a hypothesis about the behavior of the far wings of allowed absorptions.

The experimental spectra herein and others previously published were used to predict the radiative transfer in a dry CO2 model of the lower atmosphere of Venus. To cover wavelengths greater than 18.5μ, a synthetic spectrum of absorption (with terms proportional to density and to density squared) was prepared. The results indicate that the radiation balance in the lower atmosphere of Venus is adequately explained by a dry massive atmosphere of CO2 with a layer of infrared-opaque clouds. The new absorptions in the 2.3μ region are significant to this conclusion, as without them there is not enough opacity to sustain Venus' 768K surface temperature.

Appendices include summaries of CO2 properties and vibrational levels, a proposal for simplified labeling of members of Fermi multiplets, calculation of atomic polarizability derivatives, an analysis of the effect of mechanical anharmonocity, and a discussion of relative strengths of hot bands based on the radial wavefunctions for ν2 and l.

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BibTeX Citation

  author={Moore, J. A.},
  title={Infrared Absorption of Carbon Dioxide at High Densities with Application to the Atmosphere of Venus},
  school={Columbia University},
  address={New York},

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RIS Citation

ID  - mo04100g
AU  - Moore, J. A.
PY  - 1971
BT  - Infrared Absorption of Carbon Dioxide at High Densities with Application to the Atmosphere of Venus
PB  - Columbia University
CY  - New York
ER  -

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