NO Absorption Research Articles

Compact, Fast Cavity Ring-Down Spectroscopy Monitor for Simultaneous Measurement of Ozone and Nitrogen Dioxide in the Atmosphere

A sensitive, compact detector for the simultaneous measurement of O3 and NO2 is presented in this work. There are two channels in the detector, namely the Ox channel and the NO2 channel. In the presence of excess NO, ambient O3 is converted to NO2 in the Ox measurement channel. In both channels, NO2 is directly detected via cavity ring-down spectroscopy (CRDS) at 409 nm. At a 10 s integration time, the Ox and NO2 channels have a 1σ precision of 14.5 and 13.5 pptv, respectively. The Allan deviation plot shows that the optimal sensitivity of O3 and NO2 occurs at an integration time of ~60 s, with values of 10.2 and 8.5 pptv, respectively. The accuracy is 6% for the O3 channel and 5% for the NO2 channel, and the largest uncertainty comes from the effective NO2 absorption cross-section. Intercomparison of the NO2 detection between the NO2 and Ox channels shows good agreement within their uncertainties, with an absolute shift of 0.31 ppbv, a correlation coefficient of R2 = 0.99 and a slope of 0.98. Further intercomparison for ambient O3 measurement between the O3/NO2-CRDS developed in this work and a commercial UV O3 monitor also shows excellent agreement, with linear regression slopes close to unity and an R2 value of 0.99 for 1 min averaged data. The system was deployed to measure O3 and NO2 concentrations in Hefei, China, and the observation results show obvious diurnal variation characteristics. The successful deployment of the system has demonstrated that the instrument can provide a new method for retrieving fast variations in ambient O3 and NO2.

Adsorption behavior of small molecule on monolayered SiAs and sensing application for NO2 toxic gas

Owing to the ultrahigh surface-to-volume ratio and excellent carrier transport property, two-dimensional (2D) materials are regarded as most promising candidates for gas sensor with high sensitivity. Using the first principles calculations, we have examined the adsorption behavior of typical gas molecules on the 2D SiAs monolayer. The monolayered SiAs could sensitively response physical absorption of SO2, O2, NO, and NO2 molecule due to substantial charge transfer, and these molecules have introduced various defective states around the Fermi level. Most importantly, the quantum transport calculations have shown that the I–Vb behavior is substantially enhanced due to the toxic gas absorption. Specifically, striking improvement on transport performance is induced by NO2 absorption due to remarkable charge transfer, making the SiAs monolayer a promising candidate to selectively and sensitively detect NO2 molecule. Furthermore, we have shown that the work function and the charge transfer can be manipulated by strain, allowing potential application for anisotropic electronics. Our findings could be helpful to the potential application of the NO2 toxic detection in future.

A CO2-independent cloud mask from Infrared Atmospheric Sounding Interferometer (IASI) radiances for climate applications

Abstract. With more than 15 years of continuous and consistent measurements, the Infrared Atmospheric Sounding Interferometer (IASI) radiance dataset is becoming a reference climate data record. To be exploited to its full potential, it requires a cloud filter that is accurate, unbiased over the full IASI life span and strict enough to be used in satellite data retrieval schemes. Here, we present a new cloud detection algorithm which combines (1) a high sensitivity, (2) a good consistency over the whole IASI time series and between the different copies of the instrument flying on board the suite of Metop satellites, and (3) simplicity in its parametrization. The method is based on a supervised neural network (NN) and relies, as input parameters, on the IASI radiance measurements only. The robustness of the cloud mask over time is ensured in particular by avoiding the IASI channels that are influenced by CO2, N2O, CH4, CFC-11 and CFC-12 absorption lines and those corresponding to the ν2 H2O absorption band. As a reference dataset for the training, version 6.5 of the operational IASI Level 2 (L2) cloud product is used. We provide different illustrations of the NN cloud product, including comparisons with other existing products. We find very good agreement overall with version 6.5 of the operational IASI L2 with an identical mean annual cloud amount and a pixel-by-pixel correspondence of about 87 %. The comparison with the other cloud products shows a good correspondence in the main cloud regimes but with sometimes large differences in the mean cloud amount (up to 10 %) due to the specificities of each of the different products. We also show the good capability of the NN product to differentiate clouds from dust plumes.

Using Mn2+ to inhibit the adverse oxidation of sulfite solutions during the NO2 absorption: Mechanism and kinetic model

The oxidation of sulfite absorbent by oxidants in flue gas (such as O2) was one of the prime reasons hindering the NOx removal in wet flue gas denitrification technology. In this work, a novel approach to scrub NO2 was presented via adding Mn2+ to inhibit the adverse oxidation of sulfite absorbent. After adding Mn2+ in sulfite solution, NO2 removal efficiency enhanced from 90% to 98%, meanwhile, the period of efficiency >50% extended from 23 to 78 min. The absorption performance improvement and absorbent saving were attributed to the inhibition of the oxidation of SO32− by Mn2+, which was related to the hindrance on a rapid chain oxidation reaction including SO3•- with using Mn2+. Mn2+ inhibited the oxidation of SO32− by O2 via forming MnSO3 precipitation with SO32−. At the same time, Mn2+ could directly consume SO3•- to block the chain reaction of free radicals, and prevent the oxidation of SO32− by free radical. In addition, the kinetic model representing the macro absorption rate was built and this also demonstrated the favorable role of Mn2+ additive. This work provided theoretical direction for practical applications.

Effective Absorption Mechanism of SO2 and NO2 in the Flue Gas by Ammonium-Bromide-Based Deep Eutectic Solvents.

Simultaneous capture of SO2 and NOx from flue gas is critical for coal-fired power generation. In this study, environmentally friendly and high-performance deep eutectic solvents based on ethylene glycol and ammonium bromide were designed to capture SO2 and NO2 simultaneously. The SO2 and NO2 absorption performances and absorption mechanisms were systematically investigated by 1H NMR and Fourier transform infrared (FT-IR) spectroscopy in combination with ab initio calculations using Gaussian software. The results showed that EG-TBAB DESs can absorb low concentrations of SO2 and NO2 from the flue gas simultaneously at low temperatures (≤50 °C). 1H NMR, FT-IR, and simulation results indicate that SO2 and NO2 are absorbed by forming EG-TBAB-SO2–NO2 complexes, Br– is the main active site for NO2 absorption, and NO2 is more active in an EG-TBAB-NO2–SO2 complex than SO2. EG-TBAB DESs exhibit outstanding regeneration capability, and absorption capacities remain unchanged after five absorption–desorption cycles. The fundamental understanding of simultaneous capture of SO2 and NO2 from this study enables DES structures to be rationally designed for efficient and low-cost desulfurization and denitrification reagents.

A brand new two-phase wet oxidation absorption system for the simultaneous removal of SO2 and NOX from simulated marine exhaust gas

Marine engine exhaust emissions are increasingly harmful to the natural environment and human health and must be controlled. A self-synthesized amide (BAD, C12H25NO) in the laboratory shows a strong absorption capacity of nitric acid and nitrous acid, which may solve the problem that only using chlorine-based oxidant as an absorbent cannot completely absorb or retain NO2 produced by NO oxidation in previous studies. Based on Multiwfn and VMD (Visual Molecular Dynamics) program calculation, the formation mechanism of hydrogen bonds between BAD with nitric acid and nitrous acid was revealed by electrostatic potential (ESP) analysis and further confirmed by FT-IR (Fourier transform infrared spectroscopy) spectra research. Subsequently, simultaneous removal of SO2 and NOX from simulated flue gas was carried out by using NaClO/BAD as a two-phase composite absorbent, and the maximum removal efficiencies of SO2 and NOX were 98.9% and 86.6%, respectively. The recycling experiments and the engineering experiments showing that NaClO/BAD can solve the problem of absorption of NO2, and it can be a promising composite absorbent in wet desulfurization and denitrification of marine engine exhaust gas in practical applications.

The Evaluation of Urban Green Space Landscape Changes and Ecosystem Services in Beijing

As a very important part of the urban ecosystem, the urban green space system plays an active role in maintaining the urban ecosystem stability, providing ecosystem services, and improving the quality of the urban environment. In order to deal with the problems brought about by the deterioration of the urban ecological environment, it is necessary to study and analyze the spatial distribution pattern, evolutionary characteristics and ecosystem services of urban green space to maximize its ecological benefits and comprehensive functions. In this study, we took Beijing urban area as an example, and based on the spatial distribution data of urban green space and remote sensing data, we first calculated the urban green space type transition matrix, landscape pattern index and ecosystem services. Then, we analyzed the changes in urban green space landscape patterns, ecosystem services and their spatial distributions from 2000 to 2020, and studied the interactive relationships between landscape changes and changes in ecosystem services. The results showed three key findings. (1) Beijing's urban green space construction has achieved remarkable results from 2000 to 2020. The area of green space has increased by 77.41%, mainly from cultivated land and construction land. (2) From 2000 to 2020, the amounts of dust retention, SO2 absorption, NO2 absorption, cooling and humidification, carbon fixation and oxygen release, and rainwater runoff reduction in Beijing's urban green space have shown continuous increases in general. (3) There is a close relationship between urban green space landscape changes and green space ecosystem services, and total area (TA) has the highest correlation with ecosystem services. Except for rainwater runoff reduction, the correlation coefficients between TA and ecosystem services are all higher than 0.85. This research can provide theoretical guidance for optimizing Beijing's green space and determining how to maximize the effect of green space for improving the ecological environment, and ultimately provide a scientific basis for the construction of Beijing's ecological environment.

Sodium ascorbate as additive in red mud slurry for simultaneous desulfurization and denitrification: Insights into the multiple influence factors and reaction mechanism

Based on the ultra-low emission demand of SO2 and NOx in flue gas, a new absorption method was proposed to improve the desulfurization and denitrification efficiency and reduce the amount of ozone by using sodium ascorbate as an additive in red mud slurry. Compared with pure red mud slurry, the red mud (RM) + sodium ascorbate (SA) slurry significantly improved the denitrification efficiency from 24% to 84% and the desulfurization efficiency to 98%. Meanwhile, the effects of RM, SA concentration, reaction time and O3/NO molar ratio on desulfurization and denitrification efficiencies were studied. The results showed that the RM + SA composite slurry maintained high efficiencies of desulfurization and denitrification for 240 min under the optimized conditions. As an antioxidant, the introduction of SA inhibited the excessive oxidation of sulfite, and itself could easily react with NO2 through the redox reaction, greatly promoting the absorption of NO2. In addition, the reaction mechanism of the simultaneous removal of SO2 and NO2 by red mud and sodium ascorbic mixed slurry combined was proposed.

MEMS Modulator-Based Mid-Infrared Laser Heterodyne Radiometer for Atmospheric Remote Sensing

The performance of a mid-infrared laser heterodyne radiometer (MIR-LHR) based on a micro-electro-mechanical system (MEMS) mirror is demonstrated in ground-based solar occultation mode. A MEMS mirror is employed as an alternative modulator to the traditional mechanical chopper. High-resolution (∼0.0024 cm−1) transmission spectrum near 3.93 μm was obtained for atmospheric observation of N2O absorption. Operation of the MIR-LHR with laser-induced shot-noise limited performance was analyzed and experimentally achieved. The laser heterodyne spectrum obtained is consistent with Fourier-transform infrared (FT-IR) spectrometer and atmospheric transmission modeling. Compared to the traditional chopper, the MEMS mirror is smaller, lighter and lower power consumption which makes the system more stable and compact. The reported MIR-LHR in this article has great potential in aircraft instruments and satellite payloads.

Mechanism and Kinetic Study of Cyclodextrin Use to Facilitate NO2 Absorption in Sulfite Solutions.

An innovative strategy to control nitrogen oxide emission from flue gas was developed using the wet flue gas denitrification technology. The use of cyclodextrin (CD) as an additive facilitated NO2 absorption by the sulfite absorbent. Compared with absorption by a sulfite solution (59.12%), the instantaneous absorption efficiencies employing CD improved to 94.57%. Moreover, 48 h of continuous absorption indicated cyclic utilization of CD. The favorable role of CD was ascribed to facilitating the limiting step for the entire NO2 absorption-dissolution process which included both water solubility and gas-liquid mass transfer. Furthermore, we propose a potential mechanism of CD/sulfite mixed solution absorbing NO2, among which the favorable role of the additive is related to its amphiphilic behavior toward gas and liquid phases. Additionally, a kinetic model describing the rates of gas-liquid transfer and macro absorption was established based on various operating conditions. This model explains the absorption improvement in the kinetic aspect and provides theoretical guidance for practical applications.

Real-Time Monitoring of SO2 Emissions Using a UV Camera with Built-in NO2 and Aerosol Corrections.

Nitrogen dioxide (NO2) absorption correction of the sulfur dioxide (SO2) camera was demonstrated for the first time. The key to improving the measurement accuracy is to combine a differential optical absorption spectroscopy (DOAS) instrument with the SO2 camera for the real-time NO2 absorption correction and aerosol scattering correction. This method performs NO2 absorption correction by the correlation between the NO2 column density measurement of the DOAS and the NO2 optical depth of the corresponding channel from the SO2 camera at a narrow wavelength window around 310 and 310 nm. The error of correction method is estimated through comparison with only using the second channel of the traditional SO2 camera to correct for aerosol scattering and it can be reduced by 11.3% after NO2 absorption corrections. We validate the correction method through experiments and demonstrate it to be of greatly improved accuracy. The result shows that the ultraviolet (UV) SO2 camera system with NO2 absorption corrections appears to have great application prospects as a technology for visualized real-time monitoring of SO2 emissions.

The NO<sub>2</sub> camera based on gas correlation spectroscopy

Abstract. Spectroscopic methods have proven to be reliable and of high selectivity by utilizing the characteristic spectral absorption signature of trace gases such as NO2. However, they typically lack the spatiotemporal resolution required for real-time imaging measurements of NO2 emissions. We propose imaging measurements of NO2 in the visible spectral range using a novel instrument, an NO2 camera based on the principle of gas correlation spectroscopy (GCS). For this purpose two gas cells (cuvettes) are placed in front of two camera modules. One gas cell is empty, while the other is filled with a high concentration of the target gas. The filled gas cell operates as a non-dispersive spectral filter to the incoming light, maintaining the two-dimensional imaging capability of the sensor arrays. NO2 images are generated on the basis of the signal ratio between the two images in the spectral window between 430 and 445 nm, where the NO2 absorption cross section is strongly structured. The capabilities and limits of the instrument are investigated in a numerical forward model. The predictions of this model are verified in a proof-of-concept measurement, in which the column densities in specially prepared reference cells were measured with the NO2 camera and a conventional differential optical absorption spectroscopy (DOAS) instrument. Finally, results from measurements at a large power plant, the Großkraftwerk Mannheim (GKM), are presented. NO2 column densities of the plume emitted from a GKM chimney are quantified at a spatiotemporal resolution of 1/12 frames per second (FPS) and 0.9 m×0.9 m. A detection limit of 2⋅1016 molec. cm−2 was reached. An NO2 mass flux of Fm=(7.4±4.2) kg h−1 was estimated on the basis of wind speeds obtained from consecutive images. The instrument prototype is highly portable for building costs of below EUR 2000.

Assessment of NO2 Purification by Urban Forests Based on the i-Tree Eco Model: Case Study in Beijing, China

Air quality issues caused by nitrogen dioxide (NO2) have become increasingly serious in Chinese cities in recent years. As important urban green infrastructure, urban forests can mitigate gaseous nitrogen pollution by absorbing NO2 through leaf gas exchange. This study investigated spatiotemporal variations in the NO2 removal capacity of urban forests in Beijing city from 2014–2019, based on the i-Tree Eco deposition model. The results show that the annual removal capacity of administrative districts within Beijing city ranged from 14,910 to 17,747 tons, and the largest capacity (2684 tons) was found in the Fangshan district. The annual removal rate of NO2 by urban forests in administrative districts within Beijing was estimated at between 0.50–1.60 g/m2, reaching the highest (1.47 g/m2) in the Mengtougou district. The annual average absorption of NO2 by urban forests can account for 0.14–2.60% of annual total atmospheric NO2 and potentially reduce the NO2 concentration by 0.10–0.34 µg/m3 on average. The results of a principal component analysis suggest that the distribution of urban forests in Beijing is not optimized to maximize their NO2 removal capacity, being higher in suburban areas and lower in urban areas. This study provides insights into botanical NO2 removal capacity in Beijing city to mitigate atmospheric N pollution, addressing the key role of urban forests in improving human wellbeing.

Role of Sulfite Oxidation in NO2 Absorption in a pH-Neutral Scrubber Solution

Nitrogen dioxide (NO2) absorption in aqueous sulfite solutions has recently gained more attention to reduce NOx emissions. The NO2 removal efficiency is strongly influenced by the competing reactions of NO2 absorption and sulfite oxidation. The present study investigates the role of sulfite oxidation in NO2 absorption at neutral pH. The effects of sulfite concentration, thiosulfate, pH, NO2 inlet concentration, oxygen concentration on NO2 absorption efficiency, and sulfite oxidation rates were investigated under well-controlled conditions at 25 °C in a laboratory-scale wet scrubbing system. NO2 absorption rates showed a strong dependence on the sulfite concentration and increased linearly with increasing NO2 inlet concentrations between 25 and 150 ppm. At the highest investigated sulfite concentration, 20 mM, the NO2 removal efficiency was around 80%. Oxidation rates of sulfite during NO2 absorption in the presence of 5 vol % O2 increased with increasing sulfite concentrations in the scrubbing solution and ranged from 20 mg·L–1·min–1 with 1 mM sulfite to 200 mg·L–1·min–1 with 20 mM sulfite. The oxidation rate decreased significantly when thiosulfate was added, while the oxidation rates were independent of the oxygen concentration between 2–10 vol % O2. The NO2 absorption rate decreased with decreasing pH between pH 6 and 8 proportionally to the sulfite concentration as predicted by the sulfite–bisulfite equilibrium. The implication from these results is that significantly less sulfite feeding is needed in industrial NO2 absorption if the pH can be maintained at neutral pH, instead of lower pH such as in simultaneous SO2 and NO2 scrubbing.

CFD modeling for NOx absorption accompanying with SO2 in wet flue gas desulfurization scrubber based on gas-phase ozone oxidation

NOx removal performance accompanying with SO2 is investigated in a two-step process containing O3 pre-oxidation of NO and NOx post-absorption in the scrubber of wet flue gas desulfurization (WFGD) unit. Based on EulerianLagrangian framework, a comprehensive CFD model is established to describe the reactions of NO2 and N2O5 with S(IV) in droplets coupled with NOx transfer process and hydrodynamics in the scrubber. Taking the WFGD scrubber of 330 MW coal-fired power unit as case study, the results indicate NOx absorption efficiency in scrubber is increased by increasing O3/NO molar ratio from 1.0 to 2.2 and decreasing reaction temperature from 423 K to 363 K in O3 pre-oxidation process. The obtained highest removal efficiency is 85.79% for pH of 5.5 or 96.32% for pH of 9.0 in droplets. NO2 absorption is much slower than N2O5 and more sensitive to chemical compositions in droplets or hydrodynamics in scrubber. The overall mass transfer coefficient (KG) for NO2 is mainly determined by pH and S(IV) concentration in droplets, while the specific interfacial area (a) is largely influenced by gasdroplet hydrodynamics in scrubber. Finally, a correlation is proposed to predict the volumetric mass transfer coefficient (KGa) for NO2 absorption accompanying with SO2 in WFGD scrubber.

Using Mn2+ to Inhibit the Adverse Oxidation of Sulfite Solutions During the No2 Absorption: Mechanism and Kinetic Model

Using Mn2+ to Inhibit the Adverse Oxidation of Sulfite Solutions During the No2 Absorption: Mechanism and Kinetic Model

Glyoxal tropospheric column retrievals from TROPOMI – multi-satellite intercomparison and ground-based validation

Abstract. We present the first global glyoxal (CHOCHO) tropospheric column product derived from the TROPOspheric Monitoring Instrument (TROPOMI) on board the Sentinel-5 Precursor satellite. Atmospheric glyoxal results from the oxidation of other non-methane volatile organic compounds (NMVOCs) and from direct emissions caused by combustion processes. Therefore, this product is a useful indicator of VOC emissions. It is generated with an improved version of the BIRA-IASB scientific retrieval algorithm relying on the differential optical absorption spectroscopy (DOAS) approach. Among the algorithmic updates, the DOAS fit now includes corrections to mitigate the impact of spectral misfits caused by scene brightness inhomogeneity and strong NO2 absorption. The product comes along with a full error characterization, which allows for providing random and systematic error estimates for every observation. Systematic errors are typically in the range of 1 ×1014–3 ×1014 molec. cm−2 (∼30 %–70 % in emission regimes) and originate mostly from a priori data uncertainties and spectral interferences with other absorbing species. The latter may be at the origin, at least partly, of an enhanced glyoxal signal over equatorial oceans, and further investigation is needed to mitigate them. Random errors are large (>6×1014 molec. cm−2) but can be reduced by averaging observations in space and/or time. Benefiting from a high signal-to-noise ratio and a large number of small-size observations, TROPOMI provides glyoxal tropospheric column fields with an unprecedented level of detail. Using the same retrieval algorithmic baseline, glyoxal column data sets are also generated from the Ozone Monitoring Instrument (OMI) on Aura and from the Global Ozone Monitoring Experiment-2 (GOME-2) on board Metop-A and Metop-B. Those four data sets are intercompared over large-scale regions worldwide and show a high level of consistency. The satellite glyoxal columns are also compared to glyoxal columns retrieved from ground-based Multi-AXis DOAS (MAX-DOAS) instruments at nine stations in Asia and Europe. In general, the satellite and MAX-DOAS instruments provide consistent glyoxal columns both in terms of absolute values and variability. Correlation coefficients between TROPOMI and MAX-DOAS glyoxal columns range between 0.61 and 0.87. The correlation is only poorer at one mid-latitude station, where satellite data appear to be biased low during wintertime. The mean absolute glyoxal columns from satellite and MAX-DOAS generally agree well for low/moderate columns with differences of less than 1×1014 molec. cm−2. A larger bias is identified at two sites where the MAX-DOAS columns are very large. Despite this systematic bias, the consistency of the satellite and MAX-DOAS glyoxal seasonal variability is high.

Oxidation-absorption process for simultaneous removal of NOx and SO2 over Fe/Al2O3@SiO2 using vaporized H2O2

3% Fe/Al2O3 and 3% Fe/Al2O3@SiO2 were prepared to investigate the performance in simultaneous removal of NOx and SO2 using vaporized H2O2. Certain paraments were changed to explore the activity of catalysts, including temperature, H2O2 concentration, GHSV and coexistence gases component. A 24-h durability test was conducted on 3% Fe/Al2O3@SiO2. Moreover, a series of characterizations were employed to analyze the physical and chemical properties of catalysts, including XRD, BET, SEM, TEM, FTIR and XPS. Compared with 3% Fe/Al2O3, 3% Fe/Al2O3@SiO2 exhibited more excellent catalytic activity, which could achieve the peak removal efficiency of 100% for SO2 and 93.76% for NOx. Moreover, 3% Fe/Al2O3@SiO2 kept stable simultaneous removal efficiency in a 24-h test. The characterization results indicated that the BET area was greatly improved and the core-shell structure was synthesized with the formation of more micropores and mesopores by the coating of SiO2, which could improve the activity of catalyst at high temperature and high SO2 concentration. Besides, the mechanism of SO2 molecules on simultaneous removal was investigated. On one hand, a part of H2O2 was consumed by SO2 molecules without catalyst, which resulted in the drop of NOx removal by the decrease of oxidants. The main products were sulfites and bisulfites, which were broken down into SO2 over the catalyst. On the other hand, the presence of SO2 was beneficial for NOx removal by increasing oxygen vacancies on the catalyst surface and facilitating the absorption of NO2 by NaOH solution.

An improved analysis of the N2O absorption spectrum in the 1.18 µm window

A high-sensitivity absorption spectrum of natural nitrous oxide has been recorded at 10 Torr between 8321 and 8620 cm−1 (1.20 – 1.16 µm). The used cavity ring down spectrometer was referenced to a self-referenced frequency comb providing an accurate frequency scale of the spectra. The predictions of effective operator models were used for the line assignment. All identified bands correspond to the ΔP=14–16 series of transitions, where P = 2V1+V2+4V3 is the polyad number (Vi=1–3 are the vibrational quantum numbers). A total number of 3975 transitions belonging to the 14N216O, 14N15N16O, 15N14N16O,14N218O, and 15N216O isotopologues were measured with estimated accuracy better 1 × 10−3 cm−1 for most of the lines. Compared to the recent analysis of N2O spectra at 1 Torr recorded in the same region (Karlovets et al. JQSRT, 262 (2021) 107,508, doi: 10.1016/j.jqsrt.2021.107508), the higher pressure of the recordings and improved quality of the predictions have allowed to: (i) newly assign twenty-two bands, including the 4ν3 band of the 15N216O minor isotopologue, (ii) extend the assignments of previously known bands, (iii) determine the small self-induced pressure shifts of the two strongest bands (less than 10−4 cm−1) by difference of the line positions at 1 and 10 Torr and use them to obtain the zero-pressure value of the line positions, (iv) derive new or improved spectroscopic constants of 69 bands from the standard band-by-band analysis, and (v) analyze six local resonance perturbations affecting three bands, including the identification of a few extra lines due to intensity transfer. Finally, the comparison of the line positions and intensities with their predicted values and with available databases is discussed.

Experimental Research on NO2 Viscosity and Absorption for (1-Ethyl-3-methylimidazolium Trifluoroacetate + Triethanolamine) Binary Mixtures.

The viscosity (9.34–405.92 mPa·s) and absorption capacity (0.4394–1.0562 g·g−1) of (1-ethyl-3-methylidazolium trifluoroacetate + triethanolamine) binary blends atmospheric pressure in the temperature range of 303.15–343.15 K and at different mole fractions of [EMIM] [TFA] have been carried out. The molar fraction of [EMIM] [TFA] dependence of the viscosity and absorption capacity was demonstrated. The addition of a small amount of [EMIM] [TFA] into TEA led to rapidly decreased rates of binary blends’ viscosity and absorption capacity. However, the viscosity and absorption of binary blends did not decrease significantly when [EMIM] [TFA] was increased to a specific value. Compared with the molar fraction of the solution, the temperature had no obvious effect on viscosity and absorption capacity. By modeling and optimizing the ratio of viscosity and absorption capacity of ([EMIM] [TFA] + TEA), it is proven that when the mole fraction of [EMIM] [TFA] is 0.58, ([EMIM] [TFA] + TEA) has the best viscosity and absorption capacity at the same time. In addition, at 303.15 K, ([EMIM] [TFA] + TEA) was absorbed and desorbed six times, the absorption slightly decreased, and the desorption increased.