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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

A photoionization study of the formation of CO2/+/ by reaction of excited O2/+/ ions with CO

The production of CO2(+) by the ion-molecule reaction O2(+) + CO yields CO2(+) + O has been investigated using a photoionization mass spectrometer. The photoionization efficiency for production of CO2(+) by this reaction was measured from threshold at 924 A (13.42 eV) to 650 A (19.07 eV). The appearance potential corresponds to reaction of ground vibronic O2(+) ions formed in the nu-prime = 6 level. The high-vibrational-level ions of the ground ionic state are most likely produced by autoionization of O2. At wavelengths shorter than 760 A, there is a large increase in the reaction cross section associated with formation of ions in the metastable state. The peak reaction cross section occurs at 720 A.

Ajello, J. M.↗
NASA NTRS1976

Refractivities of H2, He, O2, CO, and Kr for 168-288 nm wavelength range

Precision measurements of the refractivities of H2, He, O2, CO, and Kr were made in the wavelength range 168-288 nm. By using a 1.2-m-long test cell and by keeping the test gas at accurately determined conditions near atmospheric pressure and room temperature, accuracies (90% confidence limit) were achieved for the absolute refractivities that ranged from plus or minus 0.1% to plus or minus 1.0% depending upon the gas and wavelength range. For a given gas, the ratio of refractivities at any two wavelengths has a smaller uncertainty. For H2, CO, and O2, results are for wavelengths shorter than those of previous measurements and, for He and Kr, the uncertainties are less than those of other measurements. For He refractivities agree with the theoretical ones, but in the case of H2 results are about 1% larger than the theoretical values. At the upper end of the wavelength range studied, the data are in agreement with previous measurements on H2, CO, and Kr. For O2 results indicate that the hitherto available data are too large by amounts ranging from 0.8% to 10%.

Smith, P. L.↗
NASA NTRS1977

Measurements of the O+ plus N2 and O+ plus O2 reaction rates from 300 to 900 K

Rate coefficients for the O(+) + N2 atom transfer and O(+) + O2 charge transfer reactions are determined at thermal energies between 300 K and 900 K difference in a heated drift tube mass spectrometer apparatus. At 300 K the values K(O(+) + N2) = (1.2 plus or minus 0.1) x 10 to the negative 12 power cubic cm/sec and k(O(+) + O2) = (2.1 plus or minus 0.2) x 10 to the negative 11 power cubic cm/sec were obtained, with a 50% difference decrease in the reaction rates upon heating to 700 K. These results are in good agreement with heated flowing afterglow results, but the O(+) + O2 thermal rate coefficients are systematically lower than equivalent Maxwellian rates inferred by conversion of nonthermal drift tube and flow drift data.

Chen, A.↗
NASA NTRS1979

Measurements of spectrally integrated atmospheric transmittance in the O2 Schumann-Runge bands and derived oxygen column densities - 76-102 km

Atmospheric transmittances integrated over wavelength intervals corresponding approximately to the (15-0) through (4-0) Schumann-Runge bands of O2 have been determined from EUV solar spectra (wavelengths between 1768 and 1948 A) photographed at seven altitudes between 102 and 76 km with a rocket-borne spectrograph having a resolution of 0.07 A. The observed transmittances are compared with atmospheric transmittances predicted from three models of the O2 absorption cross section. The predicted transmittances have also been used to derive column densities of atmospheric O2 from the observations. The results are compared with values calculated from the U.S. Standard Atmosphere (1976) and with oxygen column densities determined by Prinz and Brueckner (1977) from EUV solar spectra of the Schumann-Runge continuum (wavelength below 1750 A) and of the H-Lyman alpha line (1216 A) recorded on the same films used in the present research. The comparisons test the utility of the models for studies of atmospheric photochemistry, suggest which models may be best for this purpose, and indicate how the models can be improved.

Longmire, M. S.↗
NASA NTRS1980

Laboratory measurements of the O+/2D/ + N2 and O+/2D/ + O2 reaction rate coefficients and their ionospheric implications

Rate coefficients which have been measured at thermal energies for the charge transfer reactions of metastable O+/2D/ ions with N2 and O2 are reported. It is found that at an effective temperature of about 550 K, k(n2) = (8 + or - 2) x 10 to the -10 cu cm/sec and k(O2) = (7 + or - 2) x 10 to the -10 cu cm/sec. Drift tube-mass spectrometer measurements employ the reaction He(+) + O2 as the source of metastable O+ ions, showing that the ions produced in this manner are in the 2D state rather than the 2P state, a possible alternative identification. Finally, consideration is given to the ionospheric implications of the laboratory measurements.

Johnsen, R.↗
NASA NTRS1980

Charge transfer coefficients for the O+/2D/ + N2 and O+/2D/ + O2 excited ion reactions at thermal energy

An investigation of the reactions of metastable O(+) ions and O2 using drift tube-mass spectrometer techniques is presented. It was shown that ordinary charge transfer is the dominant reaction branch in both cases; it occurs with large rate coefficients, k(N2) = (8 + or - 2) x 10 to the -10th cu cm/s and k(O2) = (7 + or - 2) x 10 to the -10th cu cm/s, at an effective ion temperature of about 550 K. The reaction He(+) + O2 is used as a source of metastable O(+) ions, and evidence is presented that the O(+) ions so produced are in the 2D state rather than the 2P state. The results are compared with previous measurements, and inferences drawn from ionospheric observations.

Johnsen, R.↗
NASA NTRS1980

The kinetics of the O2/CO2 reaction in molten carbonate - Reaction orders for O2 and CO2 on NiO

The kinetics of the O2/CO2 reaction in molten carbonate is investigated using paste electrolytes and nickel sinter electrodes. A two-step approach to the determination of reaction orders is employed. First, exchange currents at various P(CO2) and P(O2) were measured using the low polarization method. Second, alpha(+) and alpha(-) values were obtained from the slope of the Allen-Hickling plot for current densities low enough so that concentration polarization within the electrode can be neglected. The reaction orders are + 1/4 in CO2 and + 5/8 in O2 in the cathodic direction, and - 3/4 in CO2 and + 1/8 in O2 in the anodic direction.

Winnick, J.↗
NASA NTRS1981

The dissociative recombination of O2/+/ in the ionosphere

Aeronomical determinations of the dissociative recombination reaction rate coefficient for O2(+) and alpha depend directly on a knowledge of the rate coefficient for the charge exchange of O(+) with O2 and k. The aeronomical determination of alpha is reevaluated using Atmosphere Explorer satellite data in light of a subsequent laboratory measurement of k (Chen et al., 1978). The results are found to be in good agreement with laboratory determinations of the coefficient for night-time conditions. For data obtained under sunlit conditions, however, the results differed significantly with those of the laboratory measurements. These results imply that the state of the O2(+) molecule major thermospheric processes needs to be examined in greater detail.

Torr, M. R.↗
NASA NTRS1985

Adsorption of O2, SO2, and SO3 on nickel oxide. Mechanism for sulfate formation

Calculations based on the atom superposition and electron delocalization molecular orbital (ASED-MO) technique suggest that O2 will adsorb perferentially end-on at an angle 45 deg from normal on a nickel cation site on the (100) surface of NiO. SO2 adsorption is also stronger on the nickel site; SO2 bonds through the sulfur atom is a plane perpendicular to the surface. Adsorption energies for SO3 on the nickel and oxygen sites are comparable in the perferred orientation in which the SO3 plane is parallel to the surface. On activation, SO3 adsorbed to an O2(-) site forms a trigonal pyramidal SO4 species which yields, with a low barrier, a tetrahedral sulfate anion. Subsequently the anion reorients on the surface. Possibilities for alternative mechanisms which require the formation of Ni3(+) or O2(-) are discussed. NiSO4 thus formed leads to the corrosion of Ni at high temperatures in the SO2+O2/SO3 The SO2+O2/SO3 atmosphere, as discussed in the experimental literature.

Mehandru, S. P.↗
NASA NTRS1985

The O2(+) vibrational distribution in the Venusian ionosphere

The vibrational distribution of O2(+) in the ionosphere of Venus was calculated for a model atmosphere (similar to one discribed by Fox, 1982), based on data from the Pioneer Venus neutral mass spectrometer. The calculation of the ion densities includes both chemistry and diffusion. At 100 km, quenching precludes survival of vibrationally excited 02(+). At the exobase, near 200 km, more than half of O2(+) molecules are vibrationally excited. The effects of vibrationally excited O2(+) on the hot oxygen coronas and the airglow are discussed.

Fox, J. L.↗
NASA NTRS1986

Adsorption of O2, SO2, and SO3, on nickel oxide - Mechanism for sulfate formation

Calculations based on the atom superposition and electron delocalization molecular orbital technique suggest that O2 will adsorb preferentially end-on at an angle 45 deg from normal on a nickel cation site on the (100) surface of NiO. SO2 adsorption is also stronger on the nickel site; SO2 bonds through the sulfur atom in a plane perpendicular to the surface. Adsorption energies for SO3 on the nickel and oxygen sites are comparable in the preferred orientation in which the SO3 plane is parallel to the surface. The calculations suggest that the strength of adsorption varies as O2 greater than SO2 greater than SO3. On activation, SO3 adsorbed to an O(2-) site forms a trigonal pyramidal SO4 species which yields, with a low barrier, a tetrahedral sulfate anion. Subsequently the anion reorients on the surface. Alternative mechanisms which require the formation of Ni(3+) or O(-) are discussed. NiSO4 thus formed may play a passivating role for the corrosion of Ni at low temperatures in the SO2 + O2 + SO3 atmospheres and an active role at high temperatures, as discussed in the experimental literature.

Mehandru, S. P.↗
NASA NTRS1986

The O2 atmospheric dayglow in the thermosphere

Spectral measurements (Delta lambda = 8A) from Spacelab 1 of the O2 atmospheric bands in the dayglow at thermospheric altitudes are reported for a tangent ray height of 150 km. Vibrational levels up to nu-prime = 4 are found in the data, requiring a source in addition to the energy transfer from O(1D) to O2. It is suggested that this source is the collisional deactivation of N(2D) by O2.

Torr, M. R.↗
NASA NTRS1986

Molecular oxygen absorption continua at 195-300 nm and O2 radiative lifetimes

With the aid of new calculations on the transition moments between the six lowest states of O2 (Klotz and Peyerimhoff, 1986), absorption cross sections have been calculated for several oxygen continua. Reasonable agreement is achieved with recent experimental results, the comparison indicating an overestimation of the theoretical transition moment for the A-X system of 20-25 percent. With this adjustment, the calculated radiative lifetime for the O2(A) state is 150 ms, in close agreement with the currently used value. The continua cross sections indicate that absorption by O2(a) cannot be a significant atmospheric process.

Saxon, R. P.↗
NASA NTRS1986

The vibrational distribution of O2(+) in the dayside ionosphere

The vibrational distributions of O2(+) in the X2Pi(g), A2Pi(u), a4Pi(u), and b4Sigma(-)g states in the dayside terrestrial ionosphere are calculated for both low and high solar activity models. The distributions are found to be significantly different from the O2(+) vibrational distributions found by Fox (1985) for the Venusian ionosphere. The sources and sinks of vibrational excitation and the implications for the chemistry, dayglow, and hot oxygen coronas are discussed. Finally, intensities of the first negative and second negative band systems of O2(+) are presented.

Fox, J. L.↗
NASA NTRS1987

Assignments of autoionization states of O2-asterisk

Attention is given to the uncertainties that remain concerning the autoionization states of O2 leading to the a 4Pi(u) and A 2Pi(u) states of O2(+), as well as some of the assignments of the autoionization states and the determinations of effective quantum numbers and quantum defects. The former problems of vibrational assignments are unambiguously established in view of a study of isotopic oxygen molecules. A systematic examination of the known Rydberg series is conducted, and new assignments and interpretations for several autoionization states leading to the various states of O2(+) are suggested.

Wu, C. Y. Robert↗
NASA NTRS1987

Mesospheric ionization and O2 1Delta(g) depletion

Observations of O2 1Delta(g) emission during solar proton events reveal large depletions below 80 and near 90 km. The lower-altitude depletions are believed to be due to odd hydrogen production and associated depletion of ozone, but the mechanism producing the depletion near 90 km has not yet been established. In this paper, it is proposed that an exothermic charge exchange reaction between O2(+) and O2 1Delta(g) is likely to be responsible for these high-altitude depletions. In particular, it is shown that the vertical structure of the observed change in airglow emission is consistent with this mechanism.

Spear, K. A.↗
NASA NTRS1988

An investigation of the second negative system of O2(+) by electron impact

Emission spectrum of O2 from 115 to 300 nm induced by electron impact at 200 eV was obtained using a crossed-beam configuration under optically thin conditions. The second negative system of O2(+) was observed in the range 186-300 nm. Model calculations were performed to derive the contribution made by the second negative system of O2(+) to auroral spectra in the same wavelength range. Observations of the spectral region from 140 to 185 nm, carried out to verify the report of Erdman and Zipf (1986) on the O or O(+) transitions showed no detectable O or O(+) transitions with a cross section upper limit of 10 to the -21 sq cm.

James, G. K.↗
NASA NTRS1989

Reaction dynamics of H + O2 at 1.6 eV collision energy

The hot hydrogen atom reaction, H + O2 yields OH + O, has been studied at a center of mass collision energy of 1.6 eV. H atoms were generated by 266 nm photolysis of HI in a mixture of HI and O2 at 293 K. The OH product was probed by laser induced fluorescence and the nascent OH vibrational, rotational, and fine structure distributions were determined. The OH(v=0/OH(v=1) vibrational branching ratio was measured to be 1.72 + or - 0.09. The data suggest that the H + O2 reaction at this collision energy proceeds via two competing mechanisms: reaction involving a long-lived complex and direct reaction.

Bronikowski, Michael J.↗