Investigation of Absorption and Emission Spectra of Nitrogen Oxides NO,N2O,NO2, and N2O4

Russian Physics Journal - The absorption and emission spectra of NO, N2O, NO2, and N2O4 nitrogen oxides have been studied with high and intermediate spectral resolution in the range 0.25–25...     

15N tracing model SimKIM to analyse the NO and N2O production during autotrophic, heterotrophic nitrification, and denitrification in soils

An adjusted model was developed to analyse measured data of nitrous oxide and nitric oxide fluxes from an arable black earth soil. The existing models for kinetic isotope studies ignore N-trace gas fluxes. The novel model includes both N-gas production by heterotrophic and autotrophic nitrification and N-gas production and consumption by denitrification. Nitrous oxide and nitric oxide production through nitrification was simulated following the 'hole-in-the-pipe' model (4: M.K. Firestone et al. Microbiological basis of NO and N2O production and consumption in soil), N-gas production by denitrification was described with first-order kinetics.The model has been evaluated in a triplicate laboratory experiment, which involved three treatments (glycine, , or -pool labeled) to distinguish the different sources of N2O and NO. Heterotrophic nitrification was negligible, whereas autotrophic nitrification and denitrification occur simultaneously in soils. Nitrification was the main source of NO and N2O in the black earth soil by field capacity (water content: 0.22 g H2O g(-1) soil). The NO release was higher than the N2O release, the N2O/NO ratio was 0.05 in this soil.     

O(1D)+N2O→NO+NO反应的理论研究

应用三体模型及扩展的LEPS势能面(PES),对初始条件为(Ecol=55 kJ/mol,v=0,j=0)的O(1D)+N2O→NO+NO反应体系进行了准经典轨线(QCT)计算.根据计算结果对体系的势能面及反应机理进行详细的分析和讨论,较全面地研究了此反应体系的动力学特征.     

An X-ray photoelectron spectroscopic study of the adsorption of N2, NH3, NO,and N2O on dysprosium

The adsorption of N₂, NH₃, NO, and N₂O onto clean polycrystalline dysprosium at 300 and 115 K and the changes undergone by the adsorbed species upon heating from 115 K have been investigated using X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). At 115 K, N₂ adsorbs dissociatively, vielding two peaks in the N 1s region at 396.2 and 398.2 eV corresponding respectively to a nitride and to chemisorbed nitrogen N(a). No peaks corresponding to molecularly adsorbed N₂ (BE 400.2 eV [10]) were observed. Upon heating the sample the N(a) is converted into the nitride species, as evidenced by a decrease in the 398.2 eV peak and a corresponding increase in the 396.2 eV peak. At a warm-up temperature of 300 K, the N(a) species accounts for only ～10% of the total nitrogen on the surface. Ammonia adsorbed at 115 K shows three distinct peaks, at 401.7, 399.3 and 396.2 eV, corresponding to molecular, partly dissociated, and completely dissociated (nitride) ammonia. Upon heating multilayer ammonia to 175 K, it desorbs to leave predominantly the peak corresponding to the partly dissociated species. Upon further heating the molecular and partly dissociated ammonia is converted into the nitride species. At 400 K only nitride-type nitrogen remains on the surface. The adsorption of NO and N₂O at 115 K is predominantly dissociative. NO has N 1s peaks at 403.1 and 396.3 eV corresponding possibly to molecularly adsorbed NO, and to nitride species. After N₂O adsorption there is very little nitrogen on the surface. Adsorption of N₂ and NO at 300 K yields only the peak at 396.2 eV, whereas NH₃ yields, in addition to this peak, a small intensity (～20%) of the peak at 398.2 eV (partly dissociated ammonia).     

CFBC混烧城市污泥与煤:N2O和NO的排放

在0.15MWth CFBC试验台上混烧城市污泥与煤,当城市污泥的含水率和混烧率分别变化在30％～60％和25％～100％之间时,可以实现稳定燃烧。分析了炉膛温度和城市污泥混烧率对NO和N_oO生成浓度的影响。结果显示,在焚烧氮含量很高的城市污泥过程中,通过适当提高炉膛温度,可以控制N_2O的生成,但是NO的生成浓度主要与混烧率有关。     

The 193 nm photolysis of NO2: NO(ν) vibrational distribution,O(1D) quantum yield and emission from vibrationally excited NO2

Time resolved Fourier transform infrared emission has been used to study the photolysis of NO2 and its dimer N2O4 at 193 nm. NO(ν) populations from the photolysis of NO2 show a bimodal distribution, peaking at ν = 5 and with a subsidiary maximum at ν = 14, close to the energetically allowed limit. The results are discussed in terms of previous measurements near this photolysis wavelength of the kinetic energies of the two possible O atomic fragments, O(3P) and O(1D), and on the electronic states of the parent molecule which can be populated. The O(1D) yield has been measured as 0.51 ± 0.04, in good agreement with previously reported values. Emission from vibrationally excited NO2 arises from the dissociation of N2O4 and is similar to that observed from photolysis at 248 nm.     

循环流化床煤燃烧中氮氧化物排放的研究

循环流化床煤燃烧中氮氧化物排放的研究冯波，袁建伟，刘皓，卢建欣，林志杰，刘德昌（华中理工大学动力系武汉４３００７４）关键词循环流化床，氮氧化物１前言近年来，ＮＺＯ由于对臭氧层的破坏作用和一定的温室效应而引起了较大的关注。特别地，在流化床煤燃烧中（包括...     

NSR催化剂12CaO-7Al2O3/10%K中水对NO还原性能的影响

主要讨论在不同反应温度和不同水蒸汽浓度下,新型的NOx储存-还原催化剂12CaO·7Al2O3／10％K(简称C12A7／K)中水的存在对NO还原性能的影响．研究结果表明,当存在1．2％水蒸汽,并低于500℃时,NO转化率和N2的选择性均降低,水蒸汽的存在对催化剂低温区的活性起到较明显的抑制作用;而温度高于500℃时,此抑制作用则基本消失,说明此时C12A7／K催化剂的水热稳定性较好．FT-IR结果证明储存NOx后的C12A7／K样品小形成了NO3／NO2的反应中间物种,用H2还原则可消除中间物种,以N2等形式放出。     

15N Analysis of nitric oxide and nitrous oxide by cryotrap enrichment using a gas chromatograph quadrupole mass spectrometer and its application to (15)N-tracer investigations of NO/N(2)O formation in soil

Nitric oxide (NO) and nitrous oxide (N(2)O) are two important trace gases in the atmosphere. Determining the concentration and (15)N abundance of NO and N(2)O in air is difficult owing to their very low concentration in the atmosphere (NO < 1 ppb(v); N(2)O approximately 0.32 ppm(v)). Although (15)N analysis of N(2)O in ambient concentrations can be carried out using a gas chromatograph quadrupole mass spectrometer system (GC-QMS) and a dosage of 2 mL of air by means of a sample loop, this system is not sensitive enough to measure the ambient concentration of NO and its (15)N abundance. Therefore the concentration of NO must be enriched by cryotrapping (cooling with liquid nitrogen). The (15)N analytical method developed enables the sensitive and sufficiently precise measurement of (15)N-enriched NO in air. Furthermore, the analytical equipment developed greatly improves existing (15)N(2)O analysis using the GC-QMS technique. An application of the (15)N analysis method will be shown for an investigation on the NO and N(2)O formation in black earth soil after (15)NH(4)(+), (15)NO(3)(-) and (15)NO(2)(-) labelling. Copyright 1999 John Wiley & Sons, Ltd.     

Additional information from the measurements by Hushfar,Rogers and Stair of the infrared chemiluminescence from the reaction N+O2 → NO+O

Hushfar et al. measured the chemiluminescent first-overtone radiation at 2.7 μm from the reaction N+O₂ → NO+O, which is followed by the fast quenching reaction N+O → N₂+O. From the rate of overtone photons per O₂ molecule and the spectrum approximated by a Boltzmann distribution, they computed ?₂, the number of overtone photons per NO-forming reaction in the low-density limit when no quenching occurs. We show ?₂ is essentially independent of the spectrum, infer the limits on the fundamental-band photon efficiency, ?₁, and obtain the initial population distribution of NO(2 ? χ ? 6).     

Analysis of the coexisting pathways for NO and N2O formation in Chernozem using the 15N-tracer SimKIM-Advanced model

The nitrogen (N) cycle consists of a variety of microbial processes. These processes often occur simultaneously in soils, but respond differently to local environmental conditions due to process-specific biochemical restrictions (e.g. oxygen levels). Hence, soil nitrogen cycling (e.g. soil N gas production through nitrification and denitrification) is individually affected through these processes, resulting in the complex and highly dynamic behaviour of total soil N turnover. The development and application of methods that facilitate the quantification of individual contributions of coexisting processes is a fundamental prerequisite for (i) understanding the dynamics of soil N turnover and (ii) implementing these processes in ecosystem models. To explain the unexpected results of the triplet tracer experiment (TTE) of Russow et al. (Role of nitrite and nitric oxide in the processes of nitrification and denitrification in soil: results from ¹⁵N tracer experiments. Soil Biol Biochem. 2009;41:785–795) the existing SimKIM model was extended to the SimKIM-Advanced model through the addition of three separate nitrite subpools associated with ammonia oxidation, oxidation of organic nitrogen (N_org), and denitrification, respectively. For the TTE, individual treatments with ¹⁵N ammonium, ¹⁵N nitrate, and ¹⁵N nitrite were conducted under oxic, hypoxic, and anoxic conditions, respectively, to clarify the role of nitric oxide as a denitrification intermediate during N₂O formation. Using a split nitrite pool, this analysis model explains the observed differences in the ¹⁵N enrichments in nitric oxide (NO) and nitrous oxide (N₂O) which occurred in dependence on different oxygen concentrations. The change from oxic over hypoxic to anoxic conditions only marginally increased the NO and N₂O release rates (1.3-fold). The analysis using the model revealed that, under oxic and hypoxic conditions, N_org-based N₂O production was the dominant pathway, contributing to 90 and 50 % of the total soil N₂O release. Under anoxic conditions, denitrification was the dominant process for soil N₂O release. The relative contribution of N_org to the total soil NO release was small. Ammonia oxidation served as the major pathway of soil NO release under oxic and hypoxic conditions, while denitrification was dominant under anoxic conditions. The model parameters for soil with moderate soil organic matter (SOM) content were not scalable to an additional data set for soil with higher SOM content, indicating a strong influence of SOM content on microbial N turnover. Thus, parameter estimation had to be re-calculated for these conditions, highlighting the necessity of individual soil-dependent parameter estimations.     

Determination of N and O – Atom and N2(A) Metastable Molecule Densities in the Afterglows of N2 and N2‐O2 Microwave Discharges

Early afterglows of N₂ and N₂‐O₂ flowing microwave discharges are characterized by optical emission spectroscopy. The N and O atom and N₂(A) metastable molecule densities are determined by optical emission spectroscopy after calibration by NO titration for N‐atoms and measurements of NO and N₂ band intensities for O‐atoms and N₂(A) metastable molecules. By using N₂ tanks with 50 and 10 ppm impurity, it is determined in the afterglow an O‐ atom impurity of 150‐200 ppm. Variations of the N and O‐atom and N₂(A) metastable molecule densities are obtained in the early afterglow of N₂–(9·10^–5–3·10^–3)O₂ gas mixtures. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

脉冲电晕放电电子能量及OH,O或O3对NO氧化的光谱学研究

采用发射光谱法测量了线板式脉冲电晕放电中激发态氮气分子N2*和离子N2+的光谱强度,并与数值计算获得的结果进行对比,确定放电电场的空间分布及平均电子能量。水平与竖直方向离开线电极0～2cm,随着距离的增加,平均电子能量和电场均呈先减后增的变化趋势;放电电场变化范围11.05～19.6MV.m-1,对应的平均电子能量的变化范围10.10～13.92eV。这一能量水平的电子足以与O2,H2O分子碰撞产生O,OH自由基,并进一步反应生成O3。在NO氧化过程中,NO可与OH自由基共存,但不能与O3共存;且O3或O氧化NO的效率高于OH自由基,推断O3或O在NO的氧化过程中起关键作用。     

On the additivity of atomic and molecular dipole properties and dispersion energies using H,N, O,H2, N2, O2, NO,N2O,NH3 and H2O as models

The zeroth-order theory of intermolecular forces is used to derive additivity relations for rotationally averaged molecular dipole properties and dispersion energy constants by assuming that a molecule is comprised of non-interacting atoms or molecules. Some of the additivity rules are new and others, for example the mixture rule for dipole oscillator strength distributions (DOSDs), Bragg's rule for stopping cross sections and Landolt's rule for molecular refractivities, are well known. The additivity rules are tested by using previously constructed DOSDs and reliable values for the dipole oscillator strength sums S_k , L_k and I_k , and dispersion energy constants C ₆, for H, N, O, H₂, N₂, O₂, NO, N₂O, NH₃ and H₂O as models. It is found that additivity is generally unreliable for estimating molecular properties corresponding to k < -2. Generally for k ≥ -2 and for C ₆, and if the hydrogen molecule is used to represent the hydrogen atom in the additivity rules, the additivity relations yield results that are reliable to within ?20 per cent and the estimates improve substantially as k increases. The effects of molecule formation on DOSDs is examined by comparing the various molecular DOSDs with the sum of the DOSDs for the atoms making up the molecules. Molecule formation results in a net decrease in the amount of dipole oscillator strength for low excitation energies and a compensating net increase for higher energies in a region extending from the absorption threshold to about 100 eV. This is shown to imply that estimates of the stopping average energy I ₀, obtained by using bona fide atomic I ₀ values, are lower bounds to the correct molecular I ₀ results.     

The oxidation of CO by O2, NO and N2O on polycrystalline platinum under knudsen conditions: A comparison

The oxidation of CO by O₂, NO and N₂O can be described by quite similar elementary reaction sequences which differ only in the way atomic oxygen is generated on the surface. This difference is sufficient to explain the observed experimental results.     

Dispersion energy constants C 6(A,B), dipole oscillator strength sums and refractivities for Li,N, O,H2, N2, O2, NH3, H2O,NO and N2O

Accurate values for the orientation-averaged long-range dipole-dipole dispersion energy coefficients, C ₆(A, B), have been determined for all possible pair interactions involving ground state H, Li, N, O, H₂, N₂, O₂, NH₃, H₂O, NO, and N₂O. The calculations have been carried out by employing dipole oscillator strength distributions for these species that have been constructed (except in the case of H) by using discrete oscillator strength, photo-absorption, and high energy inelastic scattering data and by requiring the distributions to reproduce the Thomas-Reiche-Kuhn sum rule and, in the case of the molecules, available accurate refractivity and dispersion measurements for the relevant dilute gases. These oscillator strength distributions were also used to evaluate the refractivity R(λ), as a function of wavelength λ in the visible and ultra-violet region below the ultra-violet absorption thresholds, and the dipole oscillator strength sums S _-2l , l = 1, 2, …, 7, for each atom and molecule. The calculated values of R(λ) provide refractivities for wavelengths, especially in the ultra-violet region, for which accurate experimental data are often not available. The accurate results for C ₆(A, B) and for various dipole oscillator strength sums are used to make self-consistent tests of the adequacy of (1) the C ₆(A, A) bounds provided by Padé approximant methods and (2) various semi-empirical formulae for C ₆(A, B). Some problems that can arise in using other procedures to evaluate the S _-2l and C ₆(A, B) are discussed briefly.     

Gate dielectrics prepared by double nitridation in NO and N2O

Oxynitrides prepared by double nitridation in nitric oxide (NO) and nitrous oxide (N₂O) are compared to the one with a single NO nitridation. Based on various hot-carrier stresses, harder oxide/Si interface, less charge trapping and generation of electron/hole traps in oxide, and larger charge-to-breakdown are observed for the doubly-nitrided gate dielectrics than the singly-nitrided one. By analyzing the nitrogen profiles in these oxynitrides, it is revealed that the involved mechanisms lie in the smaller distance of peak nitrogen concentration from the oxide/Si interface and the higher nitrogen content near the oxide/Si interface in the doubly-nitrided oxynitrides.     

Sensors for the nitrogen oxides, NO2, NO and N2O, based on In2O3 and WO3 nanowires

Sensing characteristics of ZnO, In₂O₃ and WO₃ nanowires have been investigated for the three nitrogen oxides, NO₂, NO and N₂O. In₂O₃ nanowires of ∼20 nm diameter prepared by using porous alumina membranes are found to have a sensitivity (defined as the ratio of the sensor resistance in the gas concerned to that in air) of about 60 for 10 ppm of all the three gases at a relatively low temperature of 150 °C. The response and recovery times are around 20 s. The sensitivity of these In₂O₃ nanowires is around 40 for 0.1 ppm of NO₂ and N₂O at 150 °C. WO₃ nanowires of 5–15 nm diameter, prepared by the solvothermal process show a sensitivity of 20–25 for 10 ppm of the three nitrogen oxides at 250 °C. The response and recovery times are 10 s and 60 s, respectively. The sensitivity is around 10 for 0.1 ppm of NO₂ at 250 °C. The sensitivity of In₂O₃ and WO₃ nanowires is not affected by humidity even up to 90% relative humidity. The study also reveals that the sensing mechanism for the three nitrogen oxides have a commonality in that the desorption of oxygen is a crucial step in all the cases. PACS 07.07.Df; 85.35.-p; 82.35.Np     

Determination of N and O‐atoms and N2 (A) Metastable Molecule Densities in the Afterglows of N2‐H2, Ar‐N2‐H2 and Ar‐N2‐O2 Microwave Discharges

Early afterglows of N₂‐H₂, Ar‐N₂‐H₂ and Ar‐N₂‐O₂ flowing microwave discharges are characterized by optical emission spectroscopy. The N and O atoms and the N₂ (A) metastable molecule densities are determined by optical emission spectroscopy after calibration by NO titration for N and O‐atoms and measurements of NO and N₂ band intensities. If an uncertainty of 30% is estimated on N‐atomic density, an inaccuracy of one order of magnitude is obtained on the O and N₂ (A) densities. In N₂‐(0.05‐2.5%)H₂ and Ar‐(1‐50%)N₂‐(0.05‐2.5%) H₂ gas mixtures, the O‐atoms are coming from O₂ impurities in the discharge. Concentrations of N and O‐atoms and of N₂ (A) densities are compared to the ones obtained in Ar‐(5‐50%)N₂‐(0.2‐2.5%) O₂ gas mixtures in which a controlled amount of O₂ is added. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

FC(O)O2的结构及其自由基与NO反应的微观机理研究

用密度泛函理论(DFT)和哈特里-福克(HF)从头计算方法和半经验势方法等研究了FC(O)O₂ 的结构和振动性质.在DFT中采用B3LYP方法,在6-311G(d)基组上对FC(O)O₂自由基与NO反应的微观过程进行了分析.首先给出了各反应物、中间体、过渡态和生成物的几何构型,然后计算了它们的能量和频率,通过频谱分析得到反应的中间体和过渡态信息,即FC(O)O₂与NO反应为多反应通道,势垒高度和反应速度给出主要通道是FC(O)O₂