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...     

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     

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

Russian Physics Journal - To the article “Investigation of Absorption and Emission Spectra of Nitrogen Oxides NO, N2O, NO2, and N2O4,” by N. I. Moskalenko, O. R. Kluchnikov, S. N....     

H-abstractions by O2, NO2, NH2, and HO2 from H2NO: Theoretical study and implications for ammonia low-temperature kinetics

Unraveling the low-temperature chemistry of ammonia is still an open challenge in combustion kinetics, yet of primary importance because of the novel combustion concepts operating in these conditions, as well as of the rising interest on ammonia as an energy carrier. In this work, a fundamental investigation of the H-abstraction reactions from H₂NO by O₂, NO₂, NH₂, and HO₂ was performed. These reactions, which belong to the radical-radical abstraction class, associate a high sensitivity to the key low temperature ammonia combustion parameters, to a high uncertainty in rate constant values. Theoretically, the investigation of reactions belonging to this class is complicated by their intrinsic multireference nature. To address this issue, a structured theoretical methodology that relies heavily on the use of CASPT2 calculations was devised. The predicted rate constants highlighted significant deviations from the rates commonly adopted in the state-of-the-art mechanisms, most often based on analogies and estimations. In order to understand their impact on ammonia low-temperature kinetics, the obtained rates were integrated into a kinetic model, which was used to investigate ammonia oxidation and ignition at low-temperature and oxygen-rich conditions. It was found that O₂ and NH₂ play the major role, as abstractors, in regulating ammonia oxidation and ignition. In particular, ignition delay time predictions proved extremely sensitive to the adopted rates: modifying each of them within their theoretical uncertainty caused deviations by even an order of magnitude, and totally changed the predictive features of the mechanism. The kinetic analysis highlighted then the need of a targeted optimization of the critical rates, downstream of the present work and within their uncertainty boundaries, to further refine the mechanism capability over a wide range of operating conditions.     

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.     

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.     

Weakly interacting molecular clusters of CO with H2O,SO2, and NO+

Intermolecular interactions in three dimers, CO···H₂O, CO···SO₂, and CO···NO⁺, were studied at the CCSD(T) level of theory, using a series of the augmented correlation consistent polarised basis sets. Interaction energy and its components as well as vibrational spectra for local minima were computed using both harmonic and anharmonic approximations. While CO···H₂O and CO···SO₂ are weakly bound with the binding energies ?7.4 and ?6.4 kJ/mol, CO···NO⁺ is much more stable with the binding energy of ?32.8 kJ/mol corresponding to ΔG = ?4.7 kJ/mol at 254 K.     

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.     

Satellite structure in the photoelectron spectra of the core electrons of NO,N2O and H2O

Satellite structures have been observed in the photoelectron spectra of the core shells of nitric oxide, nitrous oxide and water. An attempt has been made to characterize the satellite structure in terms of monopole transitions resulting from electron shake-up. For this purpose comparisons of the observed excitation energies were made with optical data for both (1) the neutral molecules and (2) the analogous equivalent-core molecular ions. Using these energy comparisons and population densities for various molecular orbitals some assignments are made of the orbitals involved in electron shake-up as a function of the core vacancy.     

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.     

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.     

Crystal Structure,Luminescence, and Triboluminescence of the Complex [Eu2(Quin)42H2O2Dipy]2(NO3)2H2O

Optics and Spectroscopy - An atomic structure of crystals of the complex [Eu2(Quin)42Н2O2Dipy]2 · 2(NO3) · Н2O, (Quin, anion of quinaldic acid; Dipy, 2,2'-dipyridyl),...     

ALGEBRAIC METHOD FOR VIBRATIONAL ENERGY SPECTRA OF H 2O AND NO 2

文内提出一种研究Ｈ２Ｏ和ＮＯ２高激发伸缩振动的Ｕ（２）代数模型,在极限条件下,该模型退化为一种非谐和耦合的局域模模型,用该模型的六个可调参数拟合实验数据,算得的标准偏差比相应的非谐和耦合的局域模型算得的偏差要小     

Photoacoustic detection of NO2 and N2O using quantum cascade lasers

Pulsed quantum cascade lasers (QCLs) with 6.2-μm and 8-μm wavelengths and a differential photoacoustic (PA) detector were used to measure concentrations of NO₂ and N₂O in the sub-ppmv range at ambient pressure. The QCL temperatures were tuned between -40 °C and 30 °C. Good agreement was found between measured PA vibrational spectra and simulated HITRAN spectra of both nitrogen oxides. The PA signals showed a linear dependence on the concentration in the investigated 0.5–50 ppmv region in both cases. The results for N₂O are compared with a PA measurement of N₂O at 2.9 μm using a grazing-incidence optical parametric oscillator. PACS 42.62.Fi; 82.80.Kq; 82.80.Gk; 92.60.Sz     

Catalytic effect of water,water dimer,water trimer,HCOOH, H2SO4, CH3CH2COOH and HN(NO2)2 on the isomerisation of HN(NO2)2 to O2NNN(O)OH: a mechanism study

In this article, the isomerisation mechanisms of HN(NO₂)₂ to O₂NNN(O)OH without and with catalyst X (X = H₂O, (H₂O)₂, (H₂O)₃, HCOOH, H₂SO₄, CH₃CH₂COOH and HN(NO₂)₂) have been investigated theoretically at the CBS-QB3 level of theory. Our results show that the catalyst X (X = H₂O, (H₂O)₂, (H₂O)₃, HCOOH, H₂SO₄ and CH₃CH₂COOH) shows different positive catalytic effects on reducing the apparent activation energy of the isomerisation reaction processes. Such different catalytic effects are mainly related to the number of hydrogen bonds and the size of the ring structure in X (X = H₂O, (H₂O)₂ and (H₂O)₃)-assisted transition states, as well as different values of pK_a for H₂SO₄, HCOOH and CH₃CH₂COOH. Very interesting is also the fact that H₂SO₄-assisted reaction is the most favourable for the hydrogen transfer from HN(NO₂)₂ to O₂NNN(O)OH, due to the smallest pK_a (?3.0) value of H₂SO₄ than H₂O, HCOOH, H₂SO₄ and CH₃CH₂COOH, and also because of the largest ∠X???H???Y (the angle between the hydrogen bond donor and acceptor) involved in H₂SO₄-assisted transition state. Compared to the self-catalysis of the isomerisation mechanisms of HN(NO₂)₂ to O₂NNN(O)OH, the apparent activation energy of H₂SO₄-assisted channel also reduces by 9.6 kcal?mol^?1, indicating that H₂SO₄ can affect the isomerisation of HN(NO₂)₂ to O₂NNN(O)OH, most obvious among all the catalysts H₂O, (H₂O)₂, (H₂O)₃, HCOOH, H₂SO₄, CH₃CH₂COOH and HN(NO₂)₂.     

Electrochemical reduction of NO and O2 on oxide based electrodes

Cyclic voltammetry has been used to investigate the electrocatalytic properties of oxide based electrodes for the reduction of NO and oxygen. Perovskites of compositions La_xSr_1-xMnO_3+δ, (LSMx), with 0.05 ≤ x ≤ 0.5 and La_0.6Sr_0.4Fe_0.8Mn_0.2O_3-δ, (LSFM), the spinels Co₃O₄ and CuCr₂O₄ and the mixed oxide V₂O₅ have been selected and investigated in the temperature range 300 – 500 °C. The materials show good catalytic properties against both NO oxidation and NO reduction. The catalytic activity as well as the selectivity is dependent both on the redox behavior of the compound and on the oxygen defect concentration. Paper presented at 7th Euroconference on Ionics, Calcatoggio, Corsica, France, Oct. 1–7, 2000.     

NO,NO2超精细LMR谱的观测

采用内腔CO激光磁共振光谱方法和微机数据采样系统,观测到了NO,NO₂分子的超精细激光磁共振(LMR)谱,简述了测量原理,给出了实验结果。