Vibrational relaxation of NO(ν=1) by oxygen atoms between 295 and 825 K -: art. no. 1109

[1] Vibrational excitation of ground-state NO through collisions with oxygen atoms produces NO(nu = 1) in the lower thermosphere, representing a significant source of atmospheric cooling through the subsequent 5.3-mum radiative emission. A laser pump-probe experiment has been used to measure the temperature dependence of the NO(nu = 1)-O vibrational relaxation rate coefficient k(O)(nu = 1) in the 295-825 K range, along with updated measurements of k(O)(nu = 1,2) at room temperature. The experiment employed a continuous wave microwave source to form O atoms, combined with photolysis of a trace amount of added NO2 to produce vibrationally excited NO. Oxygen atoms were detected through two-photon laser-induced fluorescence, cross-calibrated against a normalized O atom signal resulting from photolysis of a known concentration of NO2. No temperature dependence was observed for k(O)(v = 1) to within the uncertainty in the measurements. The measured room temperature value of k(O)(nu = 1) = (4.2 +/- 0.7) x 10(-11) cm(2) s(-1) is 75% larger than the value obtained previously in this laboratory, a significant difference at the 1sigma level. The present value is preferred owing to an improved experimental technique. The atmospherically relevant NO(nu = 0)-O vibrational excitation rate coefficient can be derived from measured values of k(O)(nu = 1) through detailed balance. The variable temperature measurements provide key information for aeronomic models of the lower thermospheric energy budget, infrared emission intensities, and neutral constituent densities.