Absorption Bands Of SO2 Research Articles

Sulfur dioxide in the mid-infrared transmission spectrum of WASP-39b.

The recent inference of sulfur dioxide (SO2) in the atmosphere of the hot (approximately 1,100 K), Saturn-mass exoplanet WASP-39b from near-infrared JWST observations1-3 suggests that photochemistry is a key process in high-temperature exoplanet atmospheres4. This is because of the low (<1 ppb) abundance of SO2 under thermochemical equilibrium compared with that produced from the photochemistry of H2O and H2S (1-10 ppm)4-9. However, the SO2 inference was made from a single, small molecular feature in the transmission spectrum of WASP-39b at 4.05 μm and, therefore, the detection of other SO2 absorption bands at different wavelengths is needed to better constrain the SO2 abundance. Here we report the detection of SO2 spectral features at 7.7 and 8.5 μm in the 5-12-μm transmission spectrum of WASP-39b measured by the JWST Mid-Infrared Instrument (MIRI) Low Resolution Spectrometer (LRS)10. Our observations suggest an abundance of SO2 of 0.5-25 ppm (1σ range), consistent with previous findings4. As well as SO2, we find broad water-vapour absorption features, as well as an unexplained decrease in the transit depth at wavelengths longer than 10 μm. Fitting the spectrum with a grid of atmospheric forward models, we derive an atmospheric heavy-element content (metallicity) for WASP-39b of approximately 7.1-8.0 times solar and demonstrate that photochemistry shapes the spectra of WASP-39b across a broad wavelength range.

An algorithm for correction of atmospheric scattering dilution effects in volcanic gas emission measurements using skylight differential optical absorption spectroscopy

Differential Optical Absorption Spectroscopy (DOAS) is commonly used to measure gas emissions from volcanoes. DOAS instruments measure the absorption of solar ultraviolet (UV) radiation scattered in the atmosphere by sulfur dioxide (SO2) and other trace gases contained in volcanic plumes. The standard spectral retrieval methods assume that all measured light comes from behind the plume and has passed through the plume along a straight line. However, a fraction of the light that reaches the instrument may have been scattered beneath the plume and thus has passed around it. Since this component does not contain the absorption signatures of gases in the plume, it effectively “dilutes” the measurements and causes underestimation of the gas abundance in the plume. This dilution effect is small for clean-air conditions and short distances between instrument and plume. However, plume measurements made at long distance and/or in conditions with significant atmospheric aerosol, haze, or clouds may be severely affected. Thus, light dilution is regarded as a major error source in DOAS measurements of volcanic degassing. Several attempts have been made to model the phenomena and the physical mechanisms are today relatively well understood. However, these models require knowledge of the local atmospheric aerosol composition and distribution, parameters that are almost always unknown. Thus, a practical algorithm to quantitatively correct for the dilution effect is still lacking. Here, we propose such an algorithm focused specifically on SO2 measurements. The method relies on the fact that light absorption becomes non-linear for high SO2 loads, and that strong and weak SO2 absorption bands are unequally affected by the diluting signal. These differences can be used to identify when dilution is occurring. Moreover, if we assume that the spectral radiance of the diluting light is identical to the spectrum of light measured away from the plume, a measured clean air spectrum can be used to represent the dilution component. A correction can then be implemented by iteratively subtracting fractions of this clean air spectrum from the measured spectrum until the respective absorption signals on strong and weak SO2 absorption bands are consistent with a single overhead SO2 abundance. In this manner, we can quantify the magnitude of light dilution in each individual measurement spectrum as well as obtaining a dilution-corrected value for the SO2 column density along the line of sight of the instrument. This paper first presents the theory behind the method, then discusses validation experiments using a radiative transfer model, as well as applications to field data obtained under different measurement conditions at three different locations; Fagradalsfjall located on the Reykjanaes peninsula in south Island, Manam located off the northeast coast of mainland Papua New Guinea and Holuhraun located in the inland of north east Island.

Ultraviolet imager on Venus orbiter Akatsuki and its initial results

The ultraviolet imager (UVI) has been developed for the Akatsuki spacecraft (Venus Climate Orbiter mission). The UVI takes ultraviolet (UV) images of the solar radiation reflected by the Venusian clouds with narrow bandpass filters centered at the 283 and 365 nm wavelengths. There are absorption bands of SO2 and unknown absorbers in these wavelength regions. The UV images provide the spatial distribution of SO2 and the unknown absorber around cloud top altitudes. The images also allow us to understand the cloud top morphologies and haze properties. Nominal sequential images with 2-h intervals are used to understand the dynamics of the Venusian atmosphere by estimating the wind vectors at the cloud top altitude, as well as the mass transportation of UV absorbers. The UVI is equipped with off-axial catadioptric optics, two bandpass filters, a diffuser installed in a filter wheel moving with a step motor, and a high sensitivity charge-coupled device with UV coating. The UVI images have spatial resolutions ranging from 200 m to 86 km at sub-spacecraft points. The UVI has been kept in good condition during the extended interplanetary cruise by carefully designed operations that have maintained its temperature maintenance and avoided solar radiation damage. The images have signal-to-noise ratios of over 100 after onboard desmear processing.

Night side distribution of SO2 content in Venus’ upper mesosphere

In this paper we present the first night side distribution of SO2 content in Venus’ upper mesosphere (altitudes from 85 to 105km). The dataset is based on the SPICAV UV stellar occultation experiment which took place onboard ESA's Venus Express (VEX) orbiter in 2006–2014. The UV channel of SPICAV spectrometer detected absorption bands of SO2 and CO2 in the spectral range 180–300nm with a resolution of 1–2nm while stellar light was occulted by the mesosphere. Altitude profiles of sulfur dioxide's volume mixing ratio (VMR) could be retrieved in the upper part of the mesosphere covering the whole night side on Venus. In parallel, we have reprocessed the terminator UV solar occultations dataset (Belyaev et al., 2012. Icarus 217, 740–751) in the same altitude range and extended its statistics until 2014. On average the SO2 VMR increases with altitude from 10–30 ppb at 85km to 100–300 ppb at 100km in both regimes of occultation. The midnight SO2 abundance appears to be 3–4 times higher than in the terminator region: 150–200ppbv versus 50pppv at altitude around 95km. These new results were compared with the distribution of oxygen atoms, which are tracers of the global subsolar-antisolar (SS-AS) circulation at ∼100km (the data provided by Soret et al., 2012 Icarus, 217, 849–855). The night time behavior looks similar for SO2 molecules and O atoms with a correlation coefficient Rcorr= 0.73. Moreover, the retrieved SO2 enrichment above 85km appears to correlate with the density of H2SO4 droplets (Luginin et al., 2016; Icarus 277, 154–170).

Ab initio determination of potential energy surfaces for the first two UV absorption bands of SO2

Three-dimensional potential energy surfaces for the two lowest singlet (Ã(1)B1 and B̃(1)A2) and two lowest triplet (ã(3)B1 and b̃(3)A2) states of SO2 have been determined at the Davidson corrected internally contracted multi-reference configuration interaction level with the augmented correlation-consistent polarized triple-zeta basis set (icMRCI+Q∕AVTZ). The non-adiabatically coupled singlet states, which are responsible for the complex Clements bands of the B band, are expressed in a 2 × 2 quasi-diabatic representation. The triplet state potential energy surfaces, which are responsible for the weak A band, were constructed in the adiabatic representation. The absorption spectrum spanning both the A and B bands, which is calculated with a three-state non-adiabatic coupled Hamiltonian, is in good agreement with experiment, thus validating the potential energy surfaces and their couplings.

A new scheme for sulphur dioxide retrieval from IASI measurements: application to the Eyjafjallajökull eruption of April and May 2010

Abstract. A new optimal estimation algorithm for the retrieval of sulphur dioxide (SO2) has been developed for the Infrared Atmospheric Sounding Interferometer (IASI) using the channels between 1000–1200 and 1300–1410 cm−1. These regions include the two SO2 absorption bands centred at about 8.7 and 7.3 μm (the ν1 and ν3 bands respectively). The retrieval assumes a Gaussian SO2 profile and returns the SO2 column amount in Dobson units and the altitude of the plume in millibars (mb). Forward modelled spectra (against which the measurements are compared) are based on the Radiative Transfer for TOVS (RTTOV) code. In our implementation RTTOV uses atmospheric profiles from European Centre for Medium-Range Weather Forecasts (ECMWF) meteorological data. The retrieval includes a comprehensive error budget for every pixel derived from an error covariance matrix that is based on the SO2-free climatology of the differences between the IASI and forward modelled spectra. The IASI forward model includes the ability to simulate a cloud or ash layer in the atmosphere. This feature is used to illustrate that: (1) the SO2 retrieval is not affected by underlying cloud but is affected if the SO2 is within or below a cloud layer; (2) it is possible to discern if ash (or other atmospheric constituents not considered in the error covariance matrix) affects the retrieval using quality control based on the fit of the measured spectrum by the forward modelled spectrum. In this work, the algorithm is applied to follow the behaviour of SO2 plumes from the Eyjafjallajökull eruption during April and May 2010. From 14 April to 4 May (during Phase I and II of the eruption) the total amount of SO2 present in the atmosphere, estimated by IASI measurements, is generally below 0.02 Tg. During the last part of the eruption (Phase III) the values are an order of magnitude higher, with a maximum of 0.18 Tg measured on the afternoon of 7 May.

Retrieval of sulphur dioxide from the infrared atmospheric sounding interferometer (IASI)

Abstract. Thermal infrared sounding of sulphur dioxide (SO2) from space has gained appreciation as a valuable complement to ultraviolet sounding. There are several strong absorption bands of SO2 in the infrared, and atmospheric sounders, such as AIRS (Atmospheric Infrared Sounder), TES (Tropospheric Emission Spectrometer) and IASI (Infrared Atmospheric Sounding Interferometer) have the ability to globally monitor SO2 abundances. Most of the observed SO2 is found in volcanic plumes. In this paper we outline a novel algorithm for the sounding of SO2 above ~5 km altitude using high resolution infrared sounders and apply it to measurements of IASI. The main features of the algorithm are a wide applicable total column range (over 4 orders of magnitude, from 0.5 to 5000 dobson units), a low theoretical uncertainty (3–5%) and near real time applicability. We make an error analysis and demonstrate the algorithm on the recent eruptions of Sarychev, Kasatochi, Grimsvötn, Puyehue-Cordón Caulle and Nabro.

Experimental examination of flame chemistry in hydrogen sulfide-based flames

Spectroscopic examination of the emission spectra of excited species in hydrogen/air flames both without and with H2S addition and in hydrogen sulfide/oxygen flame are conducted. The baseline case of hydrogen/air flame showed one distinct global peak of OH* at 309.13nm. However, higher resolution spectrum analysis showed the presence of three major OH* peaks at 306.13, 309.09, and 312.9nm. The addition of hydrogen sulfide to hydrogen/air flame resulted in the presence of a bluish cone located at inner regions of the flame. The spectrum of the blue cone showed group of peaks in the 350–470nm spectral range. The addition of H2S drastically reduced the peak value of OH* due to extensive consumption of the hydroxyl group during H2S combustion. The group of peaks in the blue cone spectrum can be divided into three major bands. The first band is formed by SO* within 320–350nm, the second band is attributed to SO3∗ within 350–400nm, and the third band is caused by H* within 400–470nm. However, the distinction of SO3∗ band and H* band around 400nm is an issue that requires further examination. Absorption bands of SH were observed at 324.03nm and 328.62nm. The effect of sulfur dioxide on the spectrum was observed by neither emission bands nor absorption bands because of its reaction with elemental oxygen to produce excited sulfur trioxide. Gas chromatography analysis showed that combustion products did not contain any SO2. The spectra of H2S/O2 flame have also been examined under lean conditions (at Φ=0.5). In contrast to H2/air/H2S flames, the spectra of H2S/O2 showed strong absorption bands of SO2 within 280–310nm. Strong continuum was observed between 280 and 460nm with distinct group of peaks superimposed in the spectra. The continuum is attributed to the afterglow of singlet and triplet SO2. The superimposed peaks are attributed to SO3∗ and H*.

Ultraviolet Absorption Spectroscopy Measurement of Trace NH3 in Gases Containing High Concentration of SO2

In heavy oil-burning thermal power plants, NH3 injection is frequently used to neutralize SOx in flue gas. In order to ascertain the neutralization effect the concentration of NH3 must be measured in the presence of high concentration of SO2. Ultraviolet absorption spectroscopy in the 200-225 nm wavelength region is the most sensitive method to measure SO2 and NH3. However, as the absorption bands of SO2 and NH3 overlap, accurate determination of the SO2 absorption is needed to detect the absorption due to trace NH3. The nonlinear dependence of the absorption coefficient on the concentration, which appeared for absorption coefficients of α>0.05 cm-1, is taken into account using a third order polynomial approximation in order to accurately determine the SO2 absorption. An analysis procedure based on this approximation was developed. Results showed that NH3 concentrations of about 4 ppm can be detected in the presence of SO2 concentrations of about 1000 ppm.

Retrieval of SO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; from thermal infrared satellite measurements: correction procedures for the effects of volcanic ash

Abstract. The simultaneous presence of SO2 and ash in a volcanic plume can lead to a significant error in the SO2 column abundance retrieval when multispectral Thermal InfraRed (TIR) data are used. The ash particles within the plume with effective radii from 1 to 10 μm reduce the Top Of Atmosphere (TOA) radiance in the entire TIR spectral range, including the channels used for SO2 retrieval. The net effect is a significant SO2 overestimation. In this work the interference of ash is discussed and two correction procedures for satellite SO2 volcanic plume retrieval in the TIR spectral range are developed to achieve an higher computational speed and a better accuracy. The ash correction can be applied when the sensor spectral range includes the 7.3 and/or 8.7 μm SO2 absorption bands, and the split window bands centered around 11 and 12 μm required for ash retrieval. This allows the possibility of simultaneous estimation of both volcanic SO2 and ash in the same data set. The proposed ash correction procedures have been applied to the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Spin Enhanced Visible and Infrared Imager (SEVIRI) measurements. Data collected during the 24 November 2006 Mt. Etna eruption have been used to illustrate the technique. The SO2 and ash estimation is carried out by using a best weighted least squares fit method and the Brightness Temperature Difference (BTD) procedures, respectively. The simulated TOA radiance Look-Up Table (LUT) needed for the SO2 column abundance and the ash retrievals have been computed using the MODTRAN 4 Radiative Transfer Model. The results show the importance of the ash correction on SO2 retrievals at 8.7 μm, where the corrected SO2 column abundance values are less than 50% of the uncorrected values. The ash correction on SO2 retrieval at 7.3 μm is much less important and only significant for low SO2 column abundances. Results also show that the simplified and faster correction procedure underestimates the ash correction compared with the more time consuming but more accurate correction procedure. Such underestimation is greater for instruments having better ground pixel resolution, i.e. greater for MODIS than for SEVIRI.

Infrared Absorption Spectroscopy Measurement of SOx using Tunable Infrared Laser

The absorption characteristics of sulfur dioxide (SO2) and sulfur trioxide (SO3) in the infrared region were measured using a quantum cascade laser and an absorption cell of length 1 m heated to 150°C. The laser was scanned over the wavelength range 6.9-7.4 μm, which included the absorption bands of SO2 and SO3. Measurement results showed that the absorption bands of SO2 and SO3 partially overlapped, with peaks at 7.28 μm and 7.35 μm for SO2 and 7.14 μm and 7.25 μm for SO3. These results showed the possbility of using infrared laser absorption spectroscopy for measurement of sulfur oxides (SOx) in flue gas. For SO3 measurement, infrared absorption spectroscopy was shown to be more suitable than ultraviolet absorption spectroscopy. The absorption characteristics of open air in the same wavelength region showed that the interference due to water vapor must be efficiently removed to perform SOx measurement in flue gas.

Detection of the SO2 Atmosphere on Io with the Hubble Space Telescope

Observations of the trailing hemisphere of Io made with the Faint Object Spectrograph of the Hubble Space Telescope in March 1992 have resulted in the first detection of atmospheric SO2 absorption bands in the ultraviolet. These observations represent only the third positive means of detection of what is widely believed to be Io's primary atmospheric constituent. Below ∼2130 Å the geometric albedo of the satellite is dominated by SO2 gas absorption band signatures, which have been analyzed using models that include the effects of optical thickness, temperature, and spatial distribution. The disk-integrated HST data cannot resolve the spatial distribution, but it is possible to define basic properties and set constraints on the atmosphere at the time of the observations, Hemispheric atmospheres with average column density N = 6-10 × 1015 cm-2 and Tgas = 110-500 K fit the data, with preference for temperatures of ∼200-250 K. Better fits are found as the atmosphere is spatially confined, with a limit of ∼8% hemispheric areal coverage and N ≈ 3 × 1017 cm-2 with colder 110-250 K temperatures. A dense (N ≥1016 cm-2), localized component of SO2 gas, such ns that possibly associated with active volcanoes, can generate the observed spectral contrast only when the atmosphere is cold (110 K) and an extended component such as Pele is included. The combination of a dense, localized atmosphere with a tenuous component (N < 1016 cm-2 either patchy or extended) also fits the data. In all cases the best fit models imply a disk-averaged column density larger than exospheric but ∼10-30 times less than the previous upper limit from near-UV observations.

On the analysis of some hyperweak absorption bands of SO2 in the regions 1055–2000 and 2200–2550 cm−1

On the analysis of some hyperweak absorption bands of SO2 in the regions 1055–2000 and 2200–2550 cm−1

Cloud chamber study of the gas phase photooxidation of sulfur dioxide

Nucleation and growth promises to be a powerful quantiative detector and amplifier for many chemical physical phenomena. We have utilized vapor phase nucleation in a study of the photo-oxidation (by disproportionation) of SO2 through adaptation of the upward diffusion cloud chamber. Our results are unique to the extent that the photolysis of SO2 is performed in the presence of high partial pressures of water vapor. At the moment (because of interference from the formation of a sulfuric acid mist) it does not seem possible to study this reaction under these conditions by any other means. Our detection scheme is based on the nucleation of water droplets by H2SO4, a product of photolysis. In these experiments H2SO4 molecules are detected in real time at concentration levels in the neighborhood of 108 cm−3, and reaction rates of the order of 108 cm−3 s−1 are also detected. The photolysis of SO2 to form SO3 and SO (by disproportionation) can result from uv excitation in either the singlet (2900 Å) or triplet (3800 Å) absorption bands of SO2. Quantitative experimental results obtained from excitation in these two respective bands (the singlet excitation leads to intersystem crossing to the triplet manifold) are entirely consistent with one another. Furthermore, the results are consistent with mechanisms previously proposed and verified for the disproporationation taking place in the absence of water vapor, with one exception. The crucial step in this mechanism involves SO2 in the 3B1 state as the principal intermediate which participates in disproportionation through a reaction with a ground state SO2 molecule. The rate constant for this step yielded by previous studies is k1a=4.2×107 l mole−1s−1 while our result is approximately 2×1011 l mole−1 s−1. This is nearly as large as the estimated collision frequency rate constant, namely, 4×1011 l mole−1 s−1. The increased rate constant in the presence of water vapor is rationalized by assuming that SO2 in our experiments, mixed with water vapor at 283% relative humidty, is hydrated so that the activated complex contains an incipient H2SO4 molecule which is stable enough to present only a negligible activation energy. By adopting a suitable strategy, our rate constants are determinable without appeal to the theory of nucleation. However, direct use of the existing theory of nucleation together with the observed rate of nucleation yields a value for the rate constant in satisfactory agreement with that derived by the means which avoids nucleation theory. In this sense our experiments also provide some confirmation of existing nucleation theory. The paper contains a detailed account of the many special technical problems (many of them solved) involved in the adaptation of the cloud chamber to the detection of chemical physical processes. In this sense the accomplishments are twofold: (1) the investigation of the gas phase photoinduced disproportionation of SO2 in the presence of water vapor, and (2) the demonstration of the use of the diffusion cloud chamber as a quantiative tool for the detection and amplification of chemical physical phenomena.

Studies on metabolism of drugs. VI. On the new metabolite of sulfisomezole in humans. 2

Biological change of sulfisomezole (N1-(5-methyl-3-isoxazole) sulfanilamide) in the human body was examined. Human urine after administration of sulfisomezole was mixed with activated charcoal, the adsorbed charcoal was eluted with ammonia-alkaline solvent, and the solvent was concentrated in a reduced pressure. The concentrated solution was passed through a column of Dowex 50-X8, the column was eluted with water, and the aqueous eluate was passed through a column of Amberlite IRA-68. The column was eluted with diluted ammonia water, the precipitate formed by the addition of lead acetate was removed, and the substance precipitated by basic lead acetate was collected by filtration. The precipitate was dissolved in ammonium sulfate solution and filtered, and the filtrate was passed through SE-Sephadex C-25 medium. The solution was neutralized with 0.1N sodium hydrogencarbonate and submitted to paper partition chromatography. The exlracted solution was passed through columns of Amberlite IRP-64 and Dowex 4, and evaporation of the effluent afforded a crystalline residue. Hydrolysis of this crystalline residue afforded sulfisomezole and glucuronic acid in 1 : 1 molar ratio. Their binding locus was examined by the comparison of Rf values of the conjugate in paper partition chromatography developed with neutral and alkaline media, study of its solubility, and the absorption bands of SO2 at 1138 and 971cm-1 in the infrared spectrum of These evidences indicated that this compound is an imide-type conjugate the glucuronic acid attached to the nitrogen in the isoxazole ring. Therefore, the biological product of sulfisomezole is a sodium sulfisomezole 2'-glucosiduronate containing 1 mole of water of crystallization.

The Infrared Spectrum and Molecular Constants of Sulfur Dioxide

By means of an infrared prism-grating spectrometer equipped with a multiple-path cell, seventeen vibration-rotation absorption bands of SO2 have been observed and recorded. Seven bands exhibiting rotational structure were analyzed for the rotational constants of the upper and lower vibrational states. Harmonic and anharmonic constants in the vibrational energy expression have been calculated, and suitable values for the force constants in a four-constant potential function have been obtained. No bands ascribable to S34O216 were found.

The near ultra-violet absorption bands of So2

The near ultra-violet absorption bands of So2