Collision-Narrowed Curves of Growth for H2 Applied to New Photoelectric Observations of Jupiter

Uwe Fink The University of Arizona, Tucson

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Michael J. S. Belton Kill Peak National Observatory, Tucson, Ariz.

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Abstract

Curves of growth suitable for the interpretation of hydrogen quadrupole lines in planetary atmospheres are calculated. Collisional narrowing of the line profile is included in the theory and it is shown how the curves of growth are affected by the phenomenon. The concept of effective pressure is analyzed. New photoelectric observations of lines in the (3—0) and (4—0) vibration-rotation bands on Jupiter are documented. An interpretation of these observations using collision-narrowed curves of growth based on both a reflecting layer and a simple scattering model atmosphere is given. The reflecting layer yields 67±17 km atm of H2 above the cloud deck at an effective temperature of 145±20K. It was not possible to deduce an effective pressure from the observations although this is shown to be possible in principle. The scattering model, which assumes isotropic scatterers, indicates 17 km atm of H2 per scattering mean free path. However, curves of growth based on this model give a very unsatisfactory fit to the data. A new spectroscopic upper limit of 40 μ of precipitable water above the cloud deck is determined.

Abstract

Curves of growth suitable for the interpretation of hydrogen quadrupole lines in planetary atmospheres are calculated. Collisional narrowing of the line profile is included in the theory and it is shown how the curves of growth are affected by the phenomenon. The concept of effective pressure is analyzed. New photoelectric observations of lines in the (3—0) and (4—0) vibration-rotation bands on Jupiter are documented. An interpretation of these observations using collision-narrowed curves of growth based on both a reflecting layer and a simple scattering model atmosphere is given. The reflecting layer yields 67±17 km atm of H2 above the cloud deck at an effective temperature of 145±20K. It was not possible to deduce an effective pressure from the observations although this is shown to be possible in principle. The scattering model, which assumes isotropic scatterers, indicates 17 km atm of H2 per scattering mean free path. However, curves of growth based on this model give a very unsatisfactory fit to the data. A new spectroscopic upper limit of 40 μ of precipitable water above the cloud deck is determined.

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