Observations have been made of non-local thermodynamic equilibrium (non-LTE) limb radiance at 923 cm-1 (10.83 μm) using the Cryogenic Limb Array Etalon Spectrometer (CLAES) aboard the Upper Atmosphere Research Satellite (UARS). We study the relative contributions from CO2 and O3 in three CLAES channels and examine the correlation with solar zenith angle. The moderate spectral resolution of CLAES allows us to discriminate the individual radiance contributions of the CO2 isotopic and O3 hot bands. The analysis shows good agreement between measured and calculated radiances and confirms our previous theoretical modeling of the non-LTE populations of these states. The diurnal variation of the measured emission points to solar dependent mechanisms selectively populating molecular vibrational levels in CO2 and O3. These processes are shown to affect the limb radiance for limb view tangent heights above about 38 km at the frequencies studied here. The measurements also show further experimental evidence for the excitation of the CO2(&ngr;3) mode by the energy transfer from electronically excited O(1D) through N2(1). This study is intended as a precursor to the inclusion of these effects in the operational CLAES data analysis. ¿ American Geophysical Union 1996