Pure rotation line emissions from highly rotationally excited OH have been observed between 80 and 110 km tangent height under both nighttime and daytime quiescent conditions. Data were obtained using the cryogenic CIRRIS 1A interferometer, operated on the Space Shuttle. Transitions from OH(v=0–2, N′≤33) were identified between 400 and 1000 cm−1, corresponding to states with energies as high as 23000 cm−1. These are the first definitive observations of OH pure rotation transitions in the air glow, and by far the highest N levels observed in any type of OH airglow emission spectrum. The present observations of highly excited rotational states of OH parallel those made during recent field studies of NO and laboratory studies of OH, NO, and CO.

Prior to the study we report here it had been thought that the sole undisturbed nighttime mechanisms for producing CO•. vibrationally excited in the v3 mode were (1) vibrational excitation by thermal collisions and (2) absorption of 4.3-um earthshine by CO•.. In this paper we show detailed evidence that the mechanism OH(v) + N•. • OH(v -1) + N•. •, followed by N•." + CO•. -• N•. + CO4v0, may be the dominant excitation mechanism for producing CO•.(v0 in the 85-km altitude region. The evidence is based on 4.3-•tm zenith radiance data obtained on April 11, 1974, via a rocket-borne liquid N•. nitrogen cooled circular variable-filtered radiometer. The rocket was launched at night from the Poker Flat Research Range, Alaska. The data were obtained under conditions of essentially zero auroral activity. There is a feature in these data near 85-km altitude which can be explained by the mechanism OH(v)• N•." • CO,(its) --} CO•. q-hp4.a,m. A column transfer of 0.12 ñ 0.025 erg/cm 2 s from OH • to N•. is required to explain the feature. An alternate explanation on the basis of just the mechanisms I and 2 which are cited above requires that there existed a very unlikely mesospheric temperature profile on the evening of April 11, 1974. A similar nonauroral feature appears consistently near 85 km in preliminary 4.3-um zenith data obtained on March 27, 1973, February 25, 1974, March 6, 1975, and March 12, 1975, thus providing further evidence that the feature most likely results from the OH mechanism rather than a strange mesopheric temperature profile. These data were obtained from the Air

A model of the production and loss of odd nitrogen species (mainly, N(4S), N(2D), NO, and NO+) and the enhanced vibration‐rotation band emission from NO in the infrared from the aurorally dosed terrestrial nighttime thermosphere is described. This model is assessed by analyzing the observations of the fundamental (Δv = −1, ∼5.3 μm) and overtone (Δv = −2, ∼2.7 μm) NO vibration‐rotation band limb emissions made by a Michelson interferometer and radiometer, respectively, aboard the Cryogenic Infrared Radiance Instrumentation for Shuttle (CIRRIS‐1A) experiment on the space shuttle Discovery during an auroral event. The auroral dosing along the line of sight is inferred from the 2.7‐μm radiance profiles using a self‐consistent procedure. The dosing obtained is then used in the model to predict the spectrally resolved emission in the 5.3‐μm region. The calculated overtone radiance profiles agree with the measured ones at lower tangent altitudes, where the signal‐to‐noise ratio is large. The calculation, however, underpredicts the observed radiance, both fundamental and overtone, at higher tangent altitudes by a factor of ∼3 and gives a colder rotational temperature for the rotationally hot component of the spectrally resolved emission from nascent NO. The causes of this discrepancy and its impact on the densities of the odd N species are discussed.

Individual OH(ν,N) rotational state population column densities have been derived from spectral analysis of CIRRIS 1A nighttime earthlimb airglow data. Both pure rotation and vibration‐rotation fundamental spectra have been examined, providing unique information on highly excited rotational states of OH(ν=0‐6). The relative populations of the four spin sublevels have also been determined. These findings provide important insights into OH dynamics at the mesopause.

Abstract. The overtone vibration-rotation band (Av=-2) limbemission from NO around 2.7 gm observed by the Cryogenic Infrared Radiance Instrumentation for Shuttle (CIRRIS-IA) at 120 km tangent altitude is shown to arise from the nascent molecule produced by the reactions of N(4S) and N(2D) atoms with 02. Measurement of the 2.7 gm emission from NO therefore permits modeling of the local rate of production of NO, a quantity important in odd nitrogen chemistry in the thermosphere. The 2.7 gm limb-radiance in the nonauroral region is observed, above the instrument noise level, only during the day and shows about a factor of 2 variation indicating a similar variation in the rate of production of NO. In the autorally dosed region however the observations lead to about an order of magnitude variation in this rate. Model of the 2.7 •tm EmissionThe overtone vibration-rotation band emission from NO around 2.7 gm may be produced by: