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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Remote sensing of atmospheric SO2 using the differential absorption LIDAR technique

The paper reports an investigation of the capabilities of a UV differential absorption lidar (DIAL) system for remote measurements of sulfur dioxide emissions. Two features of the present DIAL system are an absorption cell permitting the determination of the difference in SO2 absorption coefficients for the two transmitted wavelengths and a calibration cell permitting the linearity and performance of the system to be evaluated. The DIAL technique is described along with the transmitter, receiver, data-adquisition, and data-processing components of the investigated system. Quantitative measurements of the average SO2 concentration in a region surrounding the exhaust stack of a steam-generating plant are discussed which show that the present system has measurement sensitivities of 10 ppb at a range of 0.8 km and 20 ppb at 1.9 km. Based on performance characteristics obtained during a calibration of this system, it is predicted that a measurement sensitivity of less than 4 ppb over a 1-km path will be attained.

Hoell, J. M., Jr.↗
NASA NTRS1977

Chemiluminescent reactions of sulfur /3P2/ atoms in cryogenic matrices - S + O2 yields SO2 /a3 B1/

Results are reported for thermoluminescence studies of reactions of sulfur atoms in cryogenically deposited solid argon through in situ photolysis of OCS. Analysis of the thermoluminescence spectrum that resulted from photolysis and heating of matrices in which O2 was codeposited with an OCS/Ar mixture shows that the emitter contained oxygen derived from the added O2 and that little SO2 accumulated during photolysis. The observed absence of thermoluminescence or fluorescence in either of the allowed transitions of excited SO2 is taken as definitive evidence that ground-state sulfur atoms can insert into the oxygen molecule with effectively zero activation energy.

Long, S. R.↗
NASA NTRS1979

Fluctuations in SO2 emission during recent eruptions of Etna

The eruptive activity of July-August 1977 of Mt. Etna consisted of four separate, short eruptive episodes. The rate of SO2 emission during these eruptions was monitored using a remote-sensing correlation spectrometer. The obtained data suggest that fluctuations in the SO2 emission rate provide a means for predicting eruptions of Etna. The July-August 1977 eruptions were confined to the North East Crater vent, while continuous degassing occurred from the central vents. The continuous gas plume was blown downwind immediately after it was emitted while the eruption plumes from the North East Crater rose 500-1,000 m before being blown horizontally. Monitoring began on 24 July, immediately after the first eruptive episode had ended, and continued until 27 August.

Malinconico, L. L., Jr.↗
NASA NTRS1979

Identification of gaseous SO2 and new upper limits for other gases on Io

The identification of gaseous sulfur dioxide on Io by Voyager 1 is reported, and preliminary upper limits for other atmospheric gases are presented. Averaged spectra taken by the Voyager IRIS experiment in the range of 1,000 to 1,200/cm are interpreted as containing three fundamental sulfur dioxide bands, with intensities most nearly corresponding to an atmospheric model with a sulfur dioxide abundance of 0.2 cm atm. Upper limits for COS, CS2, SO3, H2S, CO2, O3, N2O, H2O, CH4, NH3 and HC1, not detected in the spectra, were calculated on the basis of the radiative transfer equation for temperatures of 130 and 250 K; a depletion of hydrogen, carbon and nitrogen is noted. It is suggested that a SO2 outgassing from a cooling sulfur extrusion is the major source of the observed atmospheric SO2.

Pearl, J.↗
NASA NTRS1981

IO - Could SO2 condensation/sublimation cause the sometimes reported post-eclipse brightening

It is shown that each of the three quantifiable brightening characteristics (i.e., amplitude, time-scale /half-life/, and temporal variability) suggests that brightening of Io may be due to condensation and sublimation of SO2 frost. This is concentrated within a region that encompasses both the subsolar points at the time of entrance into and emergence from eclipse, and volcanic sources. Qualitatively and intuitively, an SO2 frost hypothesis is found to provide good possibilities for explaining any variations in Io's ability to brighten, which may occur on a time scale of years.

Fanale, F. P.↗
NASA NTRS1982

Gaseous SO2 on Io

The evidence for SO2 on Io is discussed in terms of the thermal infrared and the near infrared. Recent and ongoing work in the ultraviolet is summarized. Charged particle measurements which support the presence of SO2 are presented.

Pearl, J.↗
NASA NTRS1982

Autoionization states of SO2

Assignments are reported for the autoionizing states of SO2(+) in the 1020-630 A region. The Rydberg states of SO(+) were observed by the method of molecular beam photoionization mass spectrometry, which ensures that all the states observed are autoionizing in nature. The vibrational progressions obtained are assigned to the 4b2-3s, 4b2-3d, 7a1-3p, 7a1-3d, and 2b1-3p Rydberg states. Dips in the photoionization efficiency curves of SO2(+) and SO(+) correspond to those of a window resonance series previously observed in photoabsorption.

Wu, C. Y. R.↗
NASA NTRS1982

Elastic scattering of electrons from SO2

A crossed electron beam-molecular beam scattering geometry and the relative-flow technique are used to measure the ratios of the elastic differential cross sections of SO2 to those of He at electron impact energies of 12, 20, 50, 100, 150, and 200 eV. At each energy, an angular range of 15-150 deg is covered. The ratios are multiplied by previously known He elastic differential cross sections to obtain elastic differential cross sections for SO2. Integral and momentum transfer cross sections are then determined from a knowledge of differential cross sections. With the aid of the two-potential theory of e-molecule scattering, calculations are also performed and compared with the measurements.

Orient, O. J.↗
NASA NTRS1983

Kinetics and mechanism of the oxidation of S(IV) by ozone in aqueous solution with particular reference to SO2 conversion in nonurban tropospheric clouds

Results are presented from a laboratory study of the kinetics of the S(IV)-O3 reaction in aqueous solution, including measurements of the effects of UV radiation, dissolved transition metals, and an antioxidant (hydroquinone) on the rate. On the basis of the results, relative rates of S(IV) conversion by O3 in tropospheric cloud water are compared with those predicted for H2O2 and for O2. The reaction mechanism is discussed, with an outline given of the elements of a possible reaction scheme. Application of the rate constants obtained to SO2 conversion in cloud water predicts conversion rates by ozone to be competitive with those by H2O2 at pH above about 4.5 and to dominate at pH above about 5.5. It is pointed out that since these pH's are typical for nonurban tropospheric cloud water, ozone is a potentially important contributor to the overall oxidative conversion of SO2 to sulfate in the nonurban troposphere.

Maahs, H. G.↗
NASA NTRS1984

Effects of SO2 and SO3 on the Na2SO4 induced corrosion of nickel

The effects of SO2 and SO3 in the environment on the hot-corrosion behavior of Ni in the temperature range 750-950 C has been studied. Below the melting point of Na2SO4 (884 C), rapid corrosion takes place by formation of a Na2SO4-NiSO4 melt which can penetrate the porous oxide scale and give rise to sulfide information by coming in contact with the metal. The distribution of the sulfides depends on the SO2 level in the ambient gas. Continued corrosion occurs by a sulfidation-oxidation mechanism. At temperatures above the melting point of Na2SO4, accelerated degradation occurs via dissolution of the surface scale, followed by reprecipitation of the oxide in a nonprotective form.

Misra, A. K.↗
NASA NTRS1985

The SO2 atmosphere and ionosphere of Io - Ion chemistry, atmospheric escape, and models corresponding to the Pioneer 10 radio occultation measurements

Some numerical models of the SO2 atmosphere and ionosphere of Io at the time of the Pioneer 10 fly-by are calculated. It is shown that the formation of the observed ionosphere in the downstream direction may have required the precipitation of electrons, and that solar EUV radiation alone cannot account for it. In a comparison with Pioneer 10 radio occultation measurements, an electron impact in the range 500-800 eV was found to agree with Pioneer 10 radio occultation data for a SO2 atmosphere with a surface density of 4 x 10 to the 10th per cu cm. The relatively narrow energy range and flux required for incident electrons suggests that a fraction of a torus plasma compresses the ionosphere. It is pointed out on the basis of the model calculations that a weak magnetic field may be associated with Io.

Kumar, S.↗
NASA NTRS1985

Mechanism for chelated sulfate formation from SO2 and bis (triphenylphosphine) platinum

Structure and energy surface calculations using the atom superposition and electron delocalization molecular orbital theory show that the first step in the reaction between SO2 and the dioxygen complex (PPh3)2PtO2 is the coordination of SO2 with one oxygen atom of the complex, followed by metal-oxygen bond breaking and reorientation, leading to a five-membered cyclic structure. This then rearranges to form the bidentate coordinated sulfate. Alternative pathways are considered and are found to be less favorable.

Mehandru, S. P.↗
NASA NTRS1990

The 2.5-5.0 micron spectra of Io - Evidence for H2S and H2O frozen in SO2

The present analysis of IR spectra of Io in the 2.5-5.0 micron region with laboratory data on plausible surface ices gives attention to four unidentified features exhibiting spatial and temporal band strength variations; these fall close to the fundamental stretching modes in H2S and H2O, respectively. It is suggested that the 3.85- and 3.91-micron bands in the Io spectra can be accounted for by the absorption of the S-H stretching vibration in H2S clusters and isolated molecules in an SO2-dominated ice. The observations resemble the transmission spectra of SO2 ices that contain about 3 percent H2S and 0.1 percent H2O.

Salama, F.↗
NASA NTRS1992

Differential SO2 column measurements of the Mt. Pinatubo volcanic plume

Differential SO2 column measurements of the Mt. Pinatubo volcanic plume were made from a NASA Electra aircraft flying in the Caribbean in July, 1991. The mean column content of the volcanic plume in the Caribbean was 25 micro-atm m (2.5 Dobson units) with periods of over 100 micro-atm m observed. The data indicate that an aerosol absorption or scattering effect occurs for long slant paths (low sun-elevation angles) and that 41 micro-atm m (an average obtained for 1-2 airmasses) is more representative of a true column average. Dispersion of the initial cloud from Mt. Pinatubo and a one-month SO2-to-sulfate conversion-time constant are in good agreement with the column contents found here.

Hoff, Raymond M.↗
NASA NTRS1992

Airborne observations of SO2, HCl, and O3 in the stratospheric plume of the Pinatubo volcano in July 1991

A high-resolution IR spectrometer aboard the NASA Electra aircraft to measure the total column amount of SO2, O3, and HCl above the aircraft while flying over the Caribbean three weeks after the June 15 eruption of Mt. Pinatubo in the Philippines. South of 20 deg N latitude columns of SO2 were observed ranging from 2.0-3.7 x 10 exp 16 molecules/sq cm. In addition, the column amount of HCl averaged 1.5 x 10 exp 15 molecules/sq cm in the region of the plume. This represents a small increase in HCl above the amount, estimated from the previous measurements, that would have been presented had there been no volcanic eruption, but the increase is substantially less than that seen following the 1982 eruptions of El Chichon.

Mankin, William G.↗
NASA NTRS1992

Laboratory measurements of the microwave and millimeter-wave opacity of gaseous sulfur dioxide (SO2) under simulated conditions for the Venus atmosphere

Laboratory measurements have been conducted of the opacity of gaseous SO2 in a CO2 atmosphere at 12.3 cm, 1.32 cm, and 0.32 cm, with a view to the effects of this gas on the mm-wave emission of the Venus atmosphere. Close agreement is noted between the results obtained and the absorptivity predicted from a Van Vleck-Weisskopf formalism at the two shortest wavelengths, but not at the longest. These results have been incorporated into a radiative transfer model in order to infer an abundance profile for gaseous SO2 in Venus' middle atmosphere, and are also used to ascertain the effects of a SO2/CO2 gaseous mixture on the mm-wavelength spectrum of Venus.

Fahd, Antoine K.↗
NASA NTRS1992

SO2 in the middle atmosphere of Venus: IR measurements from Venera 15 and comparison to UV

Two sets of measurements of SO2 bands in the Venus spectra are presented and compared: IR spectra obtained on the USSR Venera 15 orbiter and UV spectra from the American Pioneer Venus orbiter and sounding rockets. The 40-mbar level was chosen as a reference level for comparison. The UV data are referred to this level. There are three SO2 bands in the infrared spectrum: at 519, 1150, and 1360 cm(exp -1). The levels of their formation in the atmosphere may differ significantly, by more than 10 km.

Zasova, L. V.↗
NASA NTRS1993

SO2 on Venus: A final cross-calibration with Pioneer Venus

In the present reporting period we have met with the Pioneer Venus PI to collaborate on the recalibration of the UV spectrometer of Pioneer Venus. The associated data reduction and analysis activities have been completed. The sensitivity of the UV spectrometer has been steadily declining since orbit insertion of Pioneer Venus in 1978 due to aging of the detector tubes. The sensitivity decline is a strong function of wavelength and the rate of decline is also a function of time. Measures were taken to reduce the light dose received by the instrument to slow down the sensitivity decline. The stellar calibration using the bright UV star Hadar in 1990 indicates that the sensitivity decline may have slowed down more than have been previously estimated. The derived amount of SO2 from Pioneer Venus depends on the accuracy of the absolute sensitivity of the UV spectrometer. The previous cross calibration between IUE and Pioneer Venus led to the use of the same solar flux data for reducing and modelling data from both IUE and Pioneer Venus. The comparison between the 1991 IUE results and the Pioneer Venus stellar calibration carried out in 1990 will allow a more accurate determination of sensitivity decline of the PV UV spectrometer. The result of this comparison will be crucial in determining the trend of SO2 in the Venus atmosphere.

Stern, S. Alan↗