High Resolution Infrared Atmospheric Spectra: Solar Spectra Atlas and Laboratory Studies

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The infrared spectrum of the sun, observed through the earth's atmosphere, affords a wealth of information about atmospheric trace gases, their identities, and their amounts in the whole atmosphere when observed from ground level. The information comes in the form of individual spectrum line positions (wavelengths) in the solar spectrum, and in the intensity with which any given spectral line is absorbed from the background of the solar spectrum. Each spectrum line is a signature of some molecular or atomic species. By sensitive ground-based, or balloon-borne, spectroscopic instrumentation it is thus possible to survey the atmosphere for trace levels of gases of natural or man-made origin, and to observe changes over time. By using spectroscopic instruments of very high resolution, it is possible to observe hundreds of spectral lines representing various atmospheric trace gases, but to do this requires a detailed catalogue of precise wavelengths of the various gases present in the atmosphere, and of the solar spectrum itself as seen through the atmosphere. This grant supports an extension of research done under grants ATM-8315647 and ATM-8609286. It continues the analysis and cataloguing of spectroscopic data gathered in those earlier grants and, in its second and third years, further laboratory measurements to produce new high-resolution spectra of individual trace gases of atmospheric interest, including gases believed to affect the stratospheric ozone layer. These new data will also be analyzed and catalogued. Theoretical analyses of the complex molecular spectra will be made as an aid to identification and interpretation. This activity, while not in itself yielding new insights into physical and chemical science, yet builds an indispensible reference tool on which more probing investigations can proceed. The atlas of solar infrared spectra being developed under this grant is useful to all scientists working on the infrared spectroscopy of the sun and of the earth's atmosphere. The work will be done in a laboratory equipped with state-of-the-art spectroscopic instrumentation. This research group enjoys an international reputation for its role in advancing the application of high-resolution spectroscopy to studies of atmospheric composition.