COCHISE: Laboratory Spectroscopic Studies Of Atmospheric Phenomena With High-Sensitivity Cryogenic Instrumentation

The design of the 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, 03, CO) are formed in a low-pressure ( - 3 mtorr) environment by interaction of a flowing reactant gas with discharge--produced radical and/or metastable species; the resulting infrared radiation is detected in the absence of interference from relaxation and surface effects. A long-path optical system and cryogenic monochromator permit high sensitivity for vibrationally excited species ( - 106 molecules cm-3) and excellent spectral resolution ( 2 cm ) over the spectral range 2-16 μm. The design and operation of the facility are described in detail. Specific applications of the facility to investigations of infrared atmospheric phenomena are also discussed.