Spectra Of SO Research Articles

Study on temperature effects of broadband absorption spectroscopy based on Doppler broadening combined with a multilinear shape superposition

In this study, we determine the relationship between the broadband absorption spectroscopy and temperature using Doppler broadening combined with a multilinear shape superposition. First, a method for temperature effects on broadband absorption spectroscopy is proposed, utilizing the principle of a multiple Gaussian line shape superposition. A theoretical expression of the temperature effect on broadband spectroscopy is then presented for the first time to the best of our knowledge, and the variation law of broadband absorption spectroscopy with temperature is explained. Furthermore, the effectiveness of the expression is demonstrated by comparing experimental and theoretical data of the SO2 broadband absorption spectroscopy. The results demonstrate that the correlation coefficient (r) between the experimental and theoretical spectra of SO2 within the temperature range of 298.15–923.15 K is greater than 0.93. The method and expression presented in this Letter can effectively explain the data of previous research.

Rovibrational spectra of SO2-containing van der Waals complexes in the v1 region of SO2. Part II. SO2–H2O and SO2–D2O

Jet-cooled rovibrational absorption spectra of SO2–H2O and SO2–D2O complexes have been measured in the v1 symmetric stretching region of SO2 around 1151 cm−1 using a segmented rapid-scan quantum cascade laser spectrometer. The rovibrational spectrum of SO2–D2O has also been measured in the v2 bending region of D2O around 1178 cm−1. The tunneling splittings caused by the internal rotation of the water unit could not be resolved under our experimental conditions. The observed rovibrational transitions for these two complexes are analyzed using a standard A-reduced Watson asymmetric top Hamiltonian, yielding precise molecular constants for the excited vibrational states. The experimental band-origins are 1156.713866(70) cm−1 for SO2–H2O and 1156.819797(66) cm−1 for SO2–D2O in the v1 region of SO2, and 1180.177901(58) cm−1 for SO2–D2O in the v2 region of D2O.

Predicting molecular vibronic spectra using time-domain analog quantum simulation.

Spectroscopy is one of the most accurate probes of the molecular world. However, predicting molecular spectra accurately is computationally difficult because of the presence of entanglement between electronic and nuclear degrees of freedom. Although quantum computers promise to reduce this computational cost, existing quantum approaches rely on combining signals from individual eigenstates, an approach whose cost grows exponentially with molecule size. Here, we introduce a method for scalable analog quantum simulation of molecular spectroscopy: by performing simulations in the time domain, the number of required measurements depends on the desired spectral range and resolution, not molecular size. Our approach can treat more complicated molecular models than previous ones, requires fewer approximations, and can be extended to open quantum systems with minimal overhead. We present a direct mapping of the underlying problem of time-domain simulation of molecular spectra to the degrees of freedom and control fields available in a trapped-ion quantum simulator. We experimentally demonstrate our algorithm on a trapped-ion device, exploiting both intrinsic electronic and motional degrees of freedom, showing excellent quantitative agreement for a single-mode vibronic photoelectron spectrum of SO2.

Computational optimal transport for molecular spectra: The semi-discrete case.

Comparing a discrete molecular spectrum to a continuous molecular spectrum in a quantitative manner is a challenging problem, for example, when attempting to fit a theoretical stick spectrum to a continuous spectrum. In this paper, the use of computational optimal transport is investigated for such a problem. In the optimal transport literature, the comparison of a discrete and a continuous spectrum is referred to as semi-discrete optimal transport and is a situation where a metric such as least-squares may be difficult to define except under special conditions. The merits of an optimal transport approach for this problem are investigated using the transport distance defined for the semi-discrete case. A tutorial on semi-discrete optimal transport for molecular spectra is included in this paper, and several well-chosen synthetic spectra are investigated to demonstrate the utility of computational optimal transport for the semi-discrete case. Among several types of investigations, we include calculations showing how the frequency resolution of the continuous spectrum affects the transport distance between a discrete and a continuous spectrum. We also use the transport distance to measure the distance between a continuous experimental electronic absorption spectrum of SO2 and a theoretical stick spectrum for the same system. The comparison of the theoretical and experimental SO2 spectra also allows us to suggest a theoretical value for the band origin that is closer to the observed band origin than previous theoretical values.

Application of Excimer Lamp in Quantitative Detection of SF6 Decomposition Component SO2.

Accurate quantitative detection for trace gas has long been the center of failure diagnosis for gas-insulated equipment. An absorption spectroscopy-based detection system was developed for trace SF6 decomposition SO2 detection in this paper. In order to reduce interference from other decomposition, ultraviolet spectrum of SO2 was selected for detection. Firstly, an excimer lamp was developed in this paper as the excitation of the absorption spectroscopy compared with regular light sources with electrodes, such as electrodeless lamps that are more suitable for long-term monitoring. Then, based on the developed excimer lamp, a detection system for trace SO2 was established. Next, a proper absorption peak was selected by calculating spectral derivative for further analysis. Experimental results indicated that good linearity existed between the absorbance and concentration of SO2 at the chosen absorption peak. Moreover, the detection limit of the proposed detection system could reach the level of 10−7. The results of this paper could serve as a guide for the application of excimer lamp in online monitoring for SF6-insulated equipment.

Threshold photoelectron spectrocopy of SO2 over the photon energy range 12–50 eV

The threshold photoelectron spectra of SO2 were recorded over the photon energy range (12–50 eV) under high-resolution conditions using synchrotron radiation. Extensive vibrational ‘filling-in’ is found in the Franck-Condon gap regions between the three lowest ionic-state band systems that is attributed to autoionization of Rydberg states lying in these regions. The outer-valence ionization region (12–18 eV) consists mainly of the vibrationally well-defined electronic states of (X˜2A1), (A˜2B2), (B˜2A2), (C˜2B1), (D˜2A1) and (E˜2B2) being derived from the molecular orbitals: (8a1), (5b2), (1a2), (2b1), (7a1) and (4b2), respectively, but there are also some features that can be associated with the two weak satellite structures (1 2B1) and (3 B22). On the other hand, in the inner-valence ionization region (18–50 eV) the opposite is true, i.e., a well-defined electronic state structure is limited to the (F˜2A1) state of SO2+ with a (6a1) molecular orbital origin, with the preponderance of the remaining structure due to broad satellite features involving ionization from the inner-valence (3b2) and (5a1) molecular orbitals.

Quantitative analysis of SO2, H2S and CS2 mixed gases based on ultraviolet differential absorption spectrometry.

SO2, H2S and CS2 are the decomposition components of insulating gas SF6. The detection of these gases is significant for the online monitoring and fault diagnosis of SF6 electrical equipment. In this study, an ultraviolet differential optical absorption spectrometry (UV-DOAS) platform for detecting the concentration of SO2, H2S and CS2 mixed gases was established and a quantitatively detecting method was proposed. Firstly, the concentration of SO2 was calculated by the spectrum data at 300 nm band. Then the gas mixture spectra of H2S and CS2 at 200 nm band were obtained after linear deduction of SO2 spectrum. By wavelet extraction and fourier transform, the spectral information of H2S and CS2 was separated and the concentrations of the two gases were calculated. The method can detect the concentrations of SO2 (1-20 ppm), H2S (1-20 ppm) and CS2 (0.01-2 ppm) ternary gas mixture and the detection limits of SO2, H2S and CS2 are 0.44 ppm, 0.49 ppm and 3.23 ppb. This method has good detection sensitivity and high detection precision, which is suitable for the on-line monitoring of SF6 gas insulated equipment.

Ultraviolet differential spectroscopy quantitative analysis of SF 6 decomposition component SO 2

SO2 is a symbolic gas that can indicate the insulation status of SF6 insulation electrical equipment. Its accurate quantitative measurement is of the great significance for the judgement of the type and severity of faults inside the insulation equipment. For this reason, a detection system of trace SO2 based on ultraviolet (UV) spectrometry was presented. The measured UV absorption spectra of SO2 were processed using the wavelet analysis to remove useless spectra information and get the UV differential absorption spectra of SO2. The fast Fourier transform (FFT) was used to analyse UV differential spectra in the band of 190–230 and 290–310 nm and extract the feature information. The results show that there is a good linear relationship between the FFT characteristic peak value and the concentration of trace SO2 in the two wave bands. The detection limit in the band of 190–230 nm was even lower than that in the band of 290–310 nm. Besides, the differential absorption cross section of SO2 decreases with the increase of temperature. The study has laid a foundation for the application of the UV differential absorption spectroscopy in the online monitoring and fault diagnosis of SF6 insulation electrical equipment.

The AOTF-based NO<sub>2</sub> camera

Abstract. The abundance of NO2 in the boundary layer relates to air quality and pollution source monitoring. Observing the spatiotemporal distribution of NO2 above well-delimited (flue gas stacks, volcanoes, ships) or more extended sources (cities) allows for applications such as monitoring emission fluxes or studying the plume dynamic chemistry and its transport. So far, most attempts to map the NO2 field from the ground have been made with visible-light scanning grating spectrometers. Benefiting from a high retrieval accuracy, they only achieve a relatively low spatiotemporal resolution that hampers the detection of dynamic features. We present a new type of passive remote sensing instrument aiming at the measurement of the 2-D distributions of NO2 slant column densities (SCDs) with a high spatiotemporal resolution. The measurement principle has strong similarities with the popular filter-based SO2 camera as it relies on spectral images taken at wavelengths where the molecule absorption cross section is different. Contrary to the SO2 camera, the spectral selection is performed by an acousto-optical tunable filter (AOTF) capable of resolving the target molecule's spectral features. The NO2 camera capabilities are demonstrated by imaging the NO2 abundance in the plume of a coal-fired power plant. During this experiment, the 2-D distribution of the NO2 SCD was retrieved with a temporal resolution of 3 min and a spatial sampling of 50 cm (over a 250 × 250 m2 area). The detection limit was close to 5 × 1016 molecules cm−2, with a maximum detected SCD of 4 × 1017 molecules cm−2. Illustrating the added value of the NO2 camera measurements, the data reveal the dynamics of the NO to NO2 conversion in the early plume with an unprecedent resolution: from its release in the air, and for 100 m upwards, the observed NO2 plume concentration increased at a rate of 0.75–1.25 g s−1. In joint campaigns with SO2 cameras, the NO2 camera could also help in removing the bias introduced by the NO2 interference with the SO2 spectrum.

Molecular gas spectroscopy using radioacoustic detection and high-power coherent subterahertz radiation sources

We study the “power” approach to improve the sensitivity of the radioacoustic detection method by increasing the radiation power. A gyrotron is the source of high-power continuous monochromatic radiation in the spectrometer. As a result of analysis of experimental profiles of known lines of the rotational SO2 spectrum, it was demonstrated for the first time that an increase of radiation power by about three orders of magnitude leads to a proportional increase of the RAD spectrometer sensitivity. This permitted us, in particular, to observe the weak transitions predicted earlier in the SO2 molecule.

Theoretical assignment of the Clements bands of SO2

The photoabsorption spectrum of SO2 is theoretically investigated in the energy range 3.56–4.05eV (28713–32665cm−1). The lowest vibronic levels of the coupled excited electronic states (11A2/11B1) have been computed using Lanczos diagonalization of the Hamiltonian. The potential energy surfaces and the diabatization scheme used here were already successfully applied to describe the non-adiabatic dynamics of the molecule (Lévêque et al., 2013). The important vibronic states, playing a role in the experimental spectrum, have been analyzed according to their nodal pattern to propose the first theoretical assignment of the low-energy part of the spectrum. The Clements bands A–D have been assigned and exhibit contributions from numerous transitions, in the low resolution spectrum. The overlap of these transitions is shown to provide an “accidental” regularity of the Clements bands with respect to their intensities, while their regular energy spacing (∼220cm−1) results from a unique series (4,n2,1).

An Analysis of the High-Resolution Spectrum of the Weak v 1 +v 2 +v 3 Absorption Band of the SO2 Molecule

Sulfur dioxide is one of the most important components of the processes and phenomena studied and used for solving different problems both academic and applied. Sulfur dioxide is an important object of study in problems of air pollution control; great amounts of SO2 are emitted into the atmosphere during volcanic eruptions and as a result of human activity. Knowledge of the rotational structure of SO2 spectra is very significant for solving problems of monochromatic radiation propagation in the atmosphere, laser sensing, data transfer, etc. As a consequence, laboratory investigations of high-resolution spectra of the SO2 molecule have been carried out for many years (see, for example, [1–42]). In this paper we present the results of investigation of the v1+v2+v3 absorption band of the SO2 molecule, which had not previously been studied due to its weakness.

Study on terahertz spectra of SO2 and H2S

The spectral characteristics of air pollution gas sulfur dioxide and hydrogen sulfide has been studied experimentally and theoretically in the range of 0.2–2.6 THz. The gases absorption spectra of sulfur dioxide and hydrogen sulfide, as measured by terahertz Time-Domain Spectroscopy (THz-TDS) technique, show equi-spaced absorption peaks. The peak intervals are varied for different gas and may relate with the molecule structures and rotation modes. We have calculated the intervals of rotational transition frequency according to the gases molecule structure and the rotational modes. The results are consistent with experimental results which confirm the suggestion that the absorption is coming from the molecular rotational transition. The study suggests a technique to detect air pollutants by THz-TDS and the rotational modes of gas molecules.

Effect of HCl on Spectral Properties of Sulfur Dioxide and its Derivatives Dissolved in Water

A number of studies on sulfur dioxide (SO2) in toxicology and pharmacology have been reported, however spectral properties of SO2 and its derivatives were seldom investigated. We investigated the absorption spectra of SO2, sodium sulfite (Na2SO3), sodium bisulfite (NaHSO3) and sodium metabisulfite (Na2S2O5) in aqueous solution. In the meanwhile, the effects of HCl on spectral properties of SO2 and its derivatives were also investigated. We found that gaseous SO2 in ethanol, n-butyl-alcohol and glycerol had a characteristic absorption peak at 276 nm. Na2S2O5 and NaHSO3 exhibited an absorption peak at 257 nm. Absorption of SO2 at 276 nm was strongly enhanced in the presence of HCl. NaHSO3, Na2SO3 and Na2S2O5 also exhibited absorption at 276 nm with the addition of HCl, which was enhanced with the increase of HCl concentration. Importantly, two conclusions have been reached on the basis of our results. First, we attributed the absorbing power of SO2 to SO2 molecule, rather than hydrated sulfur dioxide. Second, absorption of SO2 strongly enhanced by HCl at 276 nm was due to H+, instead of the formation of a complex SO2Cl-. Primary studies also indicated that NaHSO3 and Na2S2O5 with HCl had a similar effect as SO2 did in rat thoracic aortic rings, which prompted us believe that NaHSO3 and Na2S2O5 with HCl may be acted as a donor of SO2 in biology and other area.

Development of multireflection absorption spectroscopy device using ultraviolet LEDs

AbstractAn ultraviolet absorption spectroscopy device using light‐emitting diodes (LEDs) as the light source was constructed. The measurement cell, light source, and transmitting and receiving optics were installed on a breadboard measuring 30 × 30 cm. A measurement optical path length of 1 m was made possible by multireflection optics. The device can mount two LEDs in tandem, and the transmitted light is coupled to an optical fiber, which is connected to a compact spectrometer. Two LEDs with center wavelengths of 280 and 295 nm were used to provide an emission spectrum which covered the peak region of the absorption spectrum of SO2 . Experiments confirmed the linearity of the absorption coefficient measured by the device for SO2 concentrations in the range of 16 to 800 ppm. © 2012 Wiley Periodicals, Inc. Electron Comm Jpn, 95(12): 62–68, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.11419

An optical system for measuring nitric oxide using spectral separation techniques

An optical sensor based on differential absorption spectroscopy for real-time monitoring of industrial nitric oxide (NO) gas emission is described. The influence of gas absorption interference from sulfur dioxide (SO2) in the environment was considered and a spectral separation technique was developed in order to eliminate this interference effect. The absorption spectrum of SO2 around 226 nm was evaluated by the SO2 concentration obtained using the experimentally recorded absorption spectrum around 300 nm. The absorption spectrum of NO around 226 nm was obtained by subtracting the absorption of SO2 from the integral absorption spectrum of SO2 and NO. The concentration measurements were performed at atmospheric pressure. The technique was found to have a lower detection limit of 0.8 ppm for NO per meter path length (SNR=2) and be immune from the influence from SO2 on the NO measurement. The sensor based on this technique was successfully employed for in situ measurement of SO2 and NO concentrations in the flue gas emitted from an industrial coal-fired boiler.

Measurement of a gas using none dispersive infrared technique with two analysis channels

In this paper, we propose a method of measuring a gas by using non-dispersive infrared (NDIR) technique with two analysis channels. The filter parameters of the two analysis channels are calculated by line-by-line integral of the selected absorption spectrum of SO2. The influences of temperature and air pressure on strengths and Lorentzian shape functions are considered accurately in the calculation. The absorption wavelengths at 7.32 μm and 4.0 μm are chosen to detect the SO2 whose concentrations are ≤qslant 280 ppm and > 280 ppm, respectively. The calibration curves of the two analysis channels are obtained by least-squares fitting two 3-order polynomials. The linearity, the sensitivity and the accuracy of the analysis system are analyzed. SO2 concentration with a large range from ～ 5 ppm to 10000 ppm can be retrieved with the measurement linearity > 0.99 and measurement error < 5%. The reasonable tradeoff is made to optimize both sensitivity and measurement range jointly. A fair balance between measurement sensitivity and large span range is obtained. Furthermore, sufficiently good measurement linearity makes cross-interference correction possible in the NDIR multi-gas analyzer.

Temporal Trends in Ambient SO<sub>2</sub> at a High Altitude Site in Semi-Arid Western India: Observations versus Chemical Transport Modeling

Ambient sulphur dioxide (SO2) measurements have been performed at a high altitude site in the semi arid region of western India, Gurushikhar, Mt. Abu (24.6°N, 72.7°E, 1680 m ASL), during different sampling periods span over Sep-Dec 2009 and Feb-Mar 2010. A global three dimensional chemical transport Model, GEOS-Chem, (v8-03-01) is employed to generate the SO2 profile for the entire region for the different sampling months which in turn is used to explain the major features in the measured SO2 spectra via correlating with HYSPLIT generated wind back trajectories. The mean SO2 concentrations recorded at the sampling site varied for the different sampling periods (4.3 ppbv in Sep-Oct 2009, 3.4 ppbv in Nov 2009, 3.5 ppbv in Dec 2009, 7.7 ppbv in Feb 2010 and 9.2 ppbv in Mar 2010) which were found to be strongly influenced by long range transport from a source region surrounding 30°N, 75°E—the one projected with the highest SO2 concentration in the GEOS-Chem generated profiles for the region—lying only a few co-ordinates away. A diurnal cycle of SO2 concentration exists throughout the sampling periods, with the greatest day-night changes observed during Feb and Mar 2010, barely detectable during Sep-Oct 2009, and intermediate values for Nov and Dec 2009 which are systematically studied using the time series PBL height and OH radical values from the GEOS-Chem model. During the sampling period in Nov 2009, a plume transport to the sampling site also was detected when a major fire erupted at an oil depot in Jaipur (26.92°N, 75.82°E), located few co-ordinates away. Separate runs of the model, performed to study the long range transport effects, show a drop in the SO2 levels over the sampling region in the absence of transport, throughout the year with Jan to Apr seen to be influenced the lowest by long range transport while Jul and Dec influenced the highest.

Development of Multireflection Absorption Spectroscopy Device using Ultraviolet LED

An ultraviolet absorption spectroscopy device using light-emitting diodes (LEDs) as the light source was constructed. The measurement cell, light source, transmitting and receiving optics were installed on a breadboard of 30 cm × 30 cm. A measurement optical path length of 1 m was made possible by multireflection optics. The device can mount two LEDs in tandem, and the transmitted light is coupled to an optical fiber, which is connected to a compact spectrometer. Here, two LEDs of center wavelengths 280 nm and 295 nm were used to provide an emission spectrum which covered the peak region of the absorption spectrum of SO2. Experiments confirmed the linearity of the absorption coefficient measured by the device for SO2 concentrations in the range 16-800 ppm.

Detailed analysis of the charge transfer complex N,N‐dimethylaniline–SO2 by Raman spectroscopy and density functional theory calculations

AbstractAlthough the amine sulfur dioxide chemistry was well characterized in the past both experimentally and theoretically, no systematic Raman spectroscopic study describes the interaction between N,N‐dimethylaniline (DMA) and sulfur dioxide (SO2). The formation of a deep red oil by the reaction of SO2 with DMA is an evidence of the charge transfer (CT) nature of the DMA–SO2 interaction. The DMA–SO2 normal Raman spectrum shows the appearance of two intense bands at 1110 and 1151 cm−1, which are enhanced when resonance is approached. These bands are assigned to νs(SO2) and ν(ϕN) vibrational modes, respectively, confirming the interaction between SO2 and the amine via the nitrogen atom. The dimethyl group steric effect favors the interaction of SO2 with the ring π electrons, which gives rise to a π–π* low‐energy CT electronic transition, as confirmed by time‐dependent density functional theory (TDDFT) calculations. In addition, the calculated Raman DMA–SO2 spectrum at the B3LYP/6‐311 + + g(3df,3pd) level shows good agreement with the experimental results (vibrational wavenumbers and relative intensities), allowing a complete assignment of the vibrational modes. A better understanding of the intermolecular interactions in this model system can be extremely useful in designing new materials to absorb, detect, or even quantify SO2. Copyright © 2009 John Wiley & Sons, Ltd.