VELOCITY DEPENDENT O-ATOM IR EXCITATION CROSS-SECTIONS - CONNECTIONS WITH FLIGHT DATA

A fast oxygen atom source has been used to study the velocity dependen ce of O atom infrared excitation reactions with various molecular spec ies in a crossed beam experiment. These short wave infrared (SWIR) mea surements are performed under single collision conditions, simulating the low Earth orbit environment. Such data are fundamental to the anal ysis and interpretation of atmospheric oxygen atom interaction with pl ume exhaust species and with the local environment about structures in low Earth orbit. Measurements have been performed over the oxygen ato m velocity range of 6 to 12 km/s. These are the first such experimenta l measurements, and they may be used to validate theoretical estimates presently used in predictive models. We specifically discuss the velo city dependent cross sections for the reaction O + N-2 --> NO(v) + N. This reaction is endothermic for O atom velocities less than or equal to 8 km/s. Preliminary data are also shown for the reaction O + CO2 -- > CO2(nu(3)) + O --> CO(v) + O-2. Both band integral and spectrally re solved results will be presented. The spectrally resolved data provide information on the rotation/vibrational distribution of the excited s tates. Limited observations of infrared emissions resulting from atmos pheric interactions have become available in recent years from both sh uttle- and rocket-borne experiments. Comparisons between our experimen tal database and selected data from several different flight experimen ts are provided. These comparisons clearly identify the kinetic mechan isms responsible for the flight observations.