Atmospheric Trace Molecule Spectroscopy

Allen, H. C J. M. Laux, R. Vogt, B. J. Finlayson-Pitts, and J. C. Hemminger, Water-Induced Reorganization of Ultrathin Nitrate Films on NaCI Implications for the Tropospheric Chemistry of Sea Salt Particles, J. Phys. Chem., 100, 6371-6375 (1996). Allen, M., and M. L. Delitsky, A Test of Odd-Oxygen Photochemistry Using Spacelab 3 Atmospheric Trace Molecule Spectroscopy Observations, J. Geophys. Res., 96, 12883-12891 (1991). 

ATMOS Atmospheric Trace Molecule Spectroscopy ST and upper Tr Oj, NO, N2Os CIONO2, HCI, HF, CHr, CFCs, etc. Space Shutde Spacelab-3 (1985), ATLAS-1,2 and 3 (1992,1993 and 1994)... 

During the last 15 years Fourier transform spectrometers have been used successfully to sound the stratosphere and upper troposphere. One of the most important successes has been the Atmospheric Trace MOlecule Spectroscopy (ATMOS) project (e.g. Farmer et al., 1987 Gunson et al., 1996). The ATMOS instrument flew aboard Spacelab 3 and the Atmospheric Laboratory for Applications and Science (ATLAS) Space Shuttle missions (Table 1). ATMOS performed solar occultation measurements and a variety of trace gases in the upper troposphere and stratosphere have been retrieved. 

The limb-tangent solar absorption method has been used to obtain profiles of trace gases in the Earth s stratosphere. An example of an investigation using this approach is the Atmospheric Trace Molecule Spectroscopy (ATMOS) Michelson interferometer carried on the Shuttle-bome Spacelab 3 in 1985. A large number of atmospheric transmission spectra were acquired in the 600 to 4700 cm spectral region (Earmer Raper, 1986 Farmer Norton, 1989). Vertical profiles of various trace gases have been obtained from these data (Park et al., 1986). 

Microwave spectroscopy is used for studyiag free radicals and ia gas analysis (30). Much laboratory work has been devoted to molecules of astrophysical iaterest (31). The technique is highly sensitive 10 mole may suffice for a spectmm. At microwave resolution, frequencies are so specific that a single line can unambiguously identify a component of a gas mixture. Tabulations of microwave transitions are available (32,33). Remote atmospheric sensing (34) is illustrated by the analysis of trace CIO, O, HO2, HCN, and N2O at the part per trillion level ia the stratosphere, usiag a ground-based millimeter-wave superheterodyne receiver at 260—280 GH2 (35). 

From the above it is clear that quantitative measurements at high sensitivities are most useful for a variety of small polar molecules which are of concern from the atmospheric environmental pollution point of view. Thus a substantial amount of effort has been and continues to be placed upon the development of field operable, portable microwave spectrometers for trace gas monitoring using both CW and FT instrumentation. Although there are likely to be continued applications of microwave spectroscopy to pure analysis problems in the future, it seems likely that the microwave spectrometer will continue to find its most exciting applications in the chemistry and physics research laboratory. 

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