Excitation of the low lying vibrational levels of H2O by O(³P) as measured on Spacelab 2

The data from the infrared telescope (IRT), which was flown on space shuttle Challenger Spacelab 2 mission (July 1985), were originally reported by Koch et al. (1987) as originating from near orbital emissions, primarily H2O. In this study, analysis of this data was extended to determine the collisional cross sections for the excitation of the low lying vibrational levels of H2O, present in the orbiter cloud, by atmospheric O(³P). The evaluation of the contribution to the measured signal from solar excitation and ram O excitation of outgassing H2O permits the determination of the H2O column density and the excitation cross section of the (010) level at an O(³P) velocity of ∼7.75 km/s. Contributions to the radiation in the 1.7-3.0 µm band by transitions from the (100), (001), and multiquantum excited levels are discussed. The findings of the study are (1) the IRT data for the 4.5-9.5 µm and the nighttime data for the 1.7-3.0 µm sensors are consistent with being explained by collision excitation of H2O by O(³P), (2) diurnal variations of 4.5-9.5 µm intensities follow the model predicted O density for a full orbit, (3) daytime increases in the H2O cloud density were not evident, (4) the cross sections for the collisional excitation process are derived and compared to values computated by Johnson (1986) and Redmon et al. (1986), (5) theoretical investigation suggests >60% of the radiation from H2O is a result of multiphoton emission resulting from collisional multiquanta excitation, and (6) the large daytime increase in the 1.7-3.0 µm intensity data suggests that O+ may likely be instrumental in producing excited H2O+ through charge exchange.

[1]  K. Westberg,et al.  Chemical Kinetic Data Sheets for High‐Temperature Chemical Reactions , 1983 .

[2]  B. Green,et al.  Infrared spectral measurement of space shuttle glow , 1992 .

[3]  E. Murad,et al.  Review of the reaction of O+ with H2O and its bearing on composition measurements from the space shuttle , 1989 .

[4]  George C. Schatz,et al.  Theoretical studies of vibrational excitation in collisions of O(3P) with H2O(1A1) , 1986 .

[5]  E. Llewellyn,et al.  The effect of temperature on shuttle glow , 1986, Nature.

[6]  J. Wolfrum,et al.  Absolute measurements of rate coefficients for the reactions of H and O atoms with H2O2 and H2O , 1971 .

[7]  Erick T. Young,et al.  Infrared observations of contaminants from shuttle flight 51-F , 1987 .

[8]  J. Crovisier.  The water molecule in comets: fluorescence mechanisms and thermodynamics of the inner coma , 1984 .

[9]  R. Wainscoat,et al.  An infrared sky model based on the IRAS point source data , 1990 .

[10]  T. Slanger.  Conjectures on the origin of the surface glow of space vehicles , 1983 .

[11]  A. Hedin.  MSIS‐86 Thermospheric Model , 1987 .

[12]  J. Futrell,et al.  A crossed beam study of the charge‐transfer reaction of Ar+ with N2 at low and intermediate energies , 1984 .

[13]  B. K. Ching,et al.  A phenomenological model of global ionospheric electron density in the E-, F1- and F2-regions , 1973 .

[14]  B. R. Johnson.  A quantum mechanical investigation of vibrational energy transfer in O(3P)+H2O collisions , 1986 .

[15]  F. W. Birss,et al.  Computer assistance in the analysis of molecular spectra: I. Rotational structure of high resolution singlet-singlet bands , 1985 .

[16]  M. Dunn,et al.  Infrared Radiation from H2O, CO2, or NH3 Collisionally Excited by N2, O, or Ar , 1974 .

[17]  M. Torr,et al.  Gas phase collisional excitation of infrared emissions in the vicinity of the space shuttle , 1988 .

[18]  Alexander Dalgarno,et al.  The surface glow of the Atmosphere Explorer C and E satellites , 1983 .

[19]  R. G. Albridge,et al.  Isotopic and vibronic coupling effects in the valence electron spectra of H2 16O, H2 18O, and D2 16O , 1975 .