COCHISE: laboratory studies of atmospheric IR chemiluminescence in a cryogenic environment

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Abstract
The design of the Cold Chemiexcitation Infrared Stimulation Experiment (COCHISE) facility, a cryogenic apparatus used for laboratory studies of high-altitude infrared excitation phenomena, is presented. The basic design concept is the extensive reduction of thermal background radiation through cryogenic (20 K) cooling of the entire reaction volume and detection system. Vibrationally excited molecules (e.g., NO, O3, CO) are formed in a low-pressure environment by interaction of a flowing reactant gas with discharge-produced radical and/or metastable species; the resulting IR radiation is detected with minimal interference from relaxation and surface effects. A long-path optical system and cryogenic monochromator permit high sensitivity for vibrationally excited species (~105 molecules cm−3) and excellent spectral resolution (~2 cm−1) over the 2–16-μm spectral range. The design and operation of the facility are described in detail. Specific applications of the facility to investigations of IR atmospheric phenomena are also discussed.