Vibrationally excited NO‡(X 2Π, v≳0) was produced by energetic electrons impacting on nitrogen–oxygen gas mixtures. The time decay of the NO‡ fundamental vibration–rotation bands in the presence of varying concentrations of N2 and O2 was measured. The quenching rate constants of NO(v=1) by N2 and O2 were determined to be kO2=2.4±1.5×10−14 and kN2=1.7±0.7×10−16 cm3 sec−1, respectively. Two quenching models are considered, independent and proportional to the vibrational level of the excited NO‡(v). If quenching of NO‡ by O2 is independent of v, the quoted rate constant kO2 becomes 75% larger. Computer intensity calculations of NO‡(Δv=1) are compared to radiometric intensity measurements. Intensity calculations using the uncertainty limits of the experimentally measured kO2 support the reliability of determined rate constants.
The vibrational temperature and molecular density of thermospheric nitrogen were probed in situ above Fort Churchill, Manitoba, Canada, on March 13, 1970. The rocket‐borne system utilized electron beam induced luminescence of the atmosphere as a diagnostic technique in effecting the measurements. The vibrational populations of N2+ ions in the B²Σu+ state were inferred from the intensities of selected transitions of the N2+ first negative (1N) band system (B²Σu+−X²Σg+) induced by a 2.5‐keV electron impact. Four narrow band photometers were used to measure the radiant intensity of the (0–1), (0–2), (1–2), and (2–4) N2+ 1N transitions. In the technique employed the vibrational population of N2(X¹Σg+) is derived from the N2+(B²Σu+, υ′ = 0 and 1) populations if it is assumed that the relative cross sections for production of the excited N2+ ions by simultaneous ionization and excitation of the neutral molecule are proportional to the appropriate Franck‐Condon factors. The inferred population of N2+(B²Σu+, υ′ = 2) is not consistent with this simple model, appearing anomalously large at low vibrational temperatures. Within the limits of uncertainty imposed by the nature of the experimental technique and by the precision realized in the measurements the inferred vibrational population ratio, [N2(υ = 1)]/[N2(υ = 0)], was not recognizably greater than that based on model atmospheric kinetic temperatures appropriate for the time of the flight (950°K exospheric temperature). An upper limit for the N2 vibrational temperature is given in the altitude range 80–175 km (1500°K at 175 km, 1200°K at 155 km, 1000°K at 135 km, and 800°K for altitudes less than 115 km). Measured N2 molecular densities are in substantial agreement (<±10% disparity) with the Jacchia (1971) model atmosphere in the 145‐ to 175‐km altitude range. At lower altitudes the measured concentrations are significantly less than the model values. For example, the measured molecular density at 120 km [2.3 × 1011 cm−3] is approximately 61% of the model value. Further departure of the results from the model at altitudes less than 120 km is attributed in part to the effects of supersonic flow about the vehicle.
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