High-temperature NO or NO2 sensor using stabilized zirconia and tungsten oxide electrode

Stabilized zirconia-based electrochemical devices for which the sensing electrode was provided with a single-metal oxide were tested for NO and NO₂ sensing properties at high temperature. Among the many single-metal oxides examined, WO₃ was found to give the best sensing properties to NO and NO₂ at 500–700°C. The EMF response of the WO₃-attached device was linear to the logarithm of NO or NO₂ concentration. The response and recovery kinetics were speedy. The device gave very small cross-sensitivities to H₂, CO, CH₄, CO₂ and water vapor. The sensing mechanism involving mixed-potential was confirmed from the measurements of polarization curves.     

Computer simulation of far infra-red peaks in liquid and glassy CH2Cl2

The observation of spectral structure in the far infra-red power absorption coefficient of molecular liquids is supported in CH₂Cl₂ by a molecular dynamics computer simulation.     

A TPD and IR study of co-adsorption of NO and oxygen on Ru(001)

The adsorption of NO on Ru(001), and its co-adsorption with oxygen, has been investigated using temperature programmed desorption and infra-red reflection-absorption spectroscopy (IRAS). Only one band due to the NO stretch of adsorbed NO could be observed and was assigned to the linearly bound v₂ species. Pre-adsorption of oxygen caused surprisingly little effect on the total desorbed flux of NO and its dissociation products in the TPD spectrum. The main effect of oxygen was to shift intensity from the v₁ peak to a new desorption peak v₁(O), which is accompanied by a splitting in the IRAS spectrum of the v₂ species. The absence of the band observed in the “bridging region” in EELS experiments and the small influence of the pre-adsorbed oxygen on the v₂ species is discussed in the light of current models for this adsorption system.     

A cw CO2 laser rangefinder using heterodyne detection and on-off amplitude modulation

A CO₂ laser rangefinder has been built that uses an acousto-optic modulator to obtain an amplitude modulated optical beam from a cw laser. An on-off deflected beam was obtained by driving the modulator with a carrier modulated by a periodic binary code. The received infra-red radiation was heterodyne detected. After envelope detection of the heterodyne signal, the signal-to-noise ratio was improved by applying a digital integrator. Ranging was carried out by calculating the delay of the received code by means of a cross-correlation technique. For this purpose a minicomputer was implemented in the system. Using 1 W average beam power and measuring times less than 1 s, ranges of several kilometers have been determined from stationary targets.     

NO分子b4Σ--a4Πi(4,0)带的吸收光谱

通过对NO与He流动混合气体放电, 产生了激发态的NO(a⁴Π_ii) 分子. 利用光外差-浓度调制吸收光谱技术测量了NO分子在12530-12850 cm^-1波段内的吸收光谱, 并标识出b⁴Σ^--a⁴Π_i(4,0)带在该波段内的324条光谱跃迁谱线. 采用标准⁴Σ^--⁴Π_i哈密顿量模型, 通过非线性最小二乘法拟合其中267条谱线, 拟合残差(0.0071 cm^-1) 接近实验系统测量误差(0.007 cm^-1). 获得的主要分子常数与文献提供的常数符合, 并且拟合得到了精细结构分子常数.     

Measurements of the electronic transition moments of C2-band systems

Electronic transition moments of seven C₂ singlet and triplet band systems, which are in the 0·2?1·2μm spectral region, have been measured. The measurements were made in emission behind incident shock waves in C₂H₂-argon mixtures. Narrow band-pass radiometers were used to obtain absolute measurements of shock-excited C₂ radiation from which absolute electronic transition moments are derived by a synthetic spectrum analysis. New results are reported for the Ballik-Ramsay, Phillips, Swan, Deslandres-d'Azambuja, Fox-Herzberg, Mulliken, and Freymark Systems.     

In-flight test of a continuous laser remote sensing system

An airborne laser system for remote sensing has been developed and tested at flight altitudes from 500 to 1200 m. The system is based on two continuous-wave CO₂ lasers (output 3 W), tunable to different wavelengths, and detects the laser radiation scattered back from earth by heterodyne reception. The feasibility of the heterodyne reception technique under aircraft environment conditions was demonstrated, and man-made SF₆ clouds and different types of uncovered minerals were traced. The data obtained indicate that the measuring range of the system can be increased to satellite distance by using a larger telescope and a more powerful laser and by reducing the electrical bandwidth. The word was supported by the German Ministry of Science and Technology, represented by DFVLR-BPT under contract number 01 TL 026-AK/RT/WRT 2074.     

被动差分光学吸收光谱法监测污染源排放总量研究

研究了一种测量污染源污染气体(如SO2、NO2)排放总量的光学遥测方法,即采用被动差分光学吸收光谱(DOAS)系统在移动平台(如汽车)上对污染源排放烟羽进行扫描测量,利用被动差分光学吸收光谱处理方法对系统采集的天顶太阳散射光谱进行处理获取柱密度,在结合测量时段的气象(风场)信息后获得污染气体的排放通量,最终得到排放总量。着重描述了获得烟羽垂直柱密度的差分光学吸收光谱方法以及污染气体排放通量的计算方法,并利用车载被动差分光学吸收光谱系统对某一热电厂SO2排放进行了外场测量,实验结果与在线设备的对比表明:这种基于被动差分光学吸收光谱光学遥测方法能够用于污染源排放总量的快速测量。     

Measurements of the electronic transition moment of the A2Π−X2Π system of ClO

The electronic transition moment of the A²Π?X²Π band system of ClO has been determined from spectral emission measurements behind incident shock waves in Cl₂-O₂ mixtures. The temperature of the radiating gas was typically 3500°K. Narrow bandpass radiometers were used to obtain absolute measurements of the ClO emission from which electronic transition moments were derived by a synthetic spectrum analysis. Absolute measurements of the O₂ Schumann-Runge system and the photo-dissociation cross section of ClO are also reported.     

B-, N-doped and BN codoped C60 heterofullerenes for environmental monitoring of NO and NO2: a DFT study

ABSTRACT

Using density functional theory calculations, we investigate the gas sensing performance of B-, N-doped and BN-codoped C₆₀ fullerenes towards NO and NO₂ molecules. The calculated adsorption energies and net charge-transfer values indicate that NO and NO₂ molecules have a stronger interaction with the BN-codoped fullerenes compared to the B- or N-doped ones. It is also found that the electronic properties of the BN-codoped C₆₀ exhibit a larger sensitivity towards NO and NO₂ molecules. An increase in the concentration of doped/co-doped B and N atoms tends to weaken the gas sensing ability of these systems.     

差分吸收光谱技术在工业污染源烟气排放监测中的应用

研究了差分吸收光谱技术在工业污染源烟气排放监测中的应用及实现.借助于独立的采样和前处理系统去除烟尘和水汽对光谱拟合的影响.为避免高浓度的SO2在常温下发生光解.将经前处理后的烟气加热至150℃进行测量.采用Voigt线型对SO2,NO,NO2在185-235 nm波段的吸收截面进行了展宽,获得了高温气体的标准吸收截面,并与归一化的光谱仪仪器函数进行卷积得到了光谱拟合所需的有效吸收截面.将反演结果与非分散红外分析仪的测量结果进行了实时对比,获得了较好的一致性,验证了差分吸收光谱方法高准确度测量工业污染源烟气排放的可行性.     

Tunable infra-red lasers and their applications to air pollution measurements

This paper describes a number of tunable infra-red lasers and techniques employing them for the detection and monitoring of gaseous air pollutants. Recent progress in the development of lasers that can be matched to characteristic infra-red absorption or emission lines of certain pollutants suggest wide potential application for sensitive specific monitoring. Examples to be described include highly-specific point-sampling,in situ source monitoring, ambient air monitoring, resonance fluorescence, and remote heterodyne detection.This work was supported by the Environmental Protection Agency.     

Absorption spectrum of the (2, 1) band in the AПi-XΣ system of CS cation

The spectrum of CS⁺ cation was recorded in the 12,235-12,600 cm⁻¹ region by employing optical heterodyne velocity modulation absorption spectroscopy. In combination with simultaneous measurement of optical heterodyne concentration modulation absorption spectroscopy, the spectral lines of CS⁺ blended with the neutral CS lines were identified and extracted from the observed spectra. One hundred and eighty-two spectral lines of CS⁺ were assigned to the (2, 1) band in the A²П_i-X²Σ⁺ system and the improved molecular constants of the upper level (υ = 2) in the A²П_i state were derived by nonlinear least squares fitting.     

Femtosecond laser-induced nonlinear spectroscopy for remote sensing of methane

Femtosecond laser-induced nonlinear molecular spectroscopy is applied for sensing atmospheric greenhouse gas methane (CH₄). The high intensity inside the Ti-sapphire femtosecond laser filaments can dissociate the CH₄ molecules into small fragments which emit characteristic fluorescence. Backward CH radical fluorescence is used to quantitatively analyze the pollutant concentration and its remote detection limit. PACS 42.68.Wt; 42.65.Jx; 95.75.Fg     

空间外差光谱自适应基线校正研究

空间外差光谱具有较高的信噪比与光谱分辨率,在大气微量气体遥感领域得到重要应用,实现基线的自适应校正是光谱预处理的重要环节。基于光谱的特点,分别采用阈值拟合法和改进的经验模态法对实测近红外水汽空间外差光谱进行基线校正。结果表明,两种方法均能实现光谱基线的自动扣除;以光谱扭曲程度及光谱相似度对两种方法的校正效果进行定量评价,阈值拟合法校正后的光谱扭曲程度及光谱相似度为0.761和0.955,改进经验模态法的结果分别为0.717和0.954,说明改进经验模态法略优。在校正方法的耗时上,改进经验模态法以其特有的算法优势仅需较少的迭代次数就能获得最终的基线光谱,完成校正,耗时不足阈值拟合法的十分之一,效率更高。     

Infra-red heterodyne laser radar for remote sensing of air pollutants by range-resolved differential absorption

An infra-red heterodyne laser radar scheme incorporating range-resolved differential absorption using elastically backscattered, pulsed signal from distributed particles in the atmosphere is proposed and analysed. The basic requirements of the system arrangement and operating parameters involved in this scheme are discussed in detail. This method is shown to offer a remote and spatially-resolved measurement of various molecuar pollutants dispersed in the air for ranges up to several km and detection sensitivities to less than 0.1 ppm with laser pulses of 100 W average power. This power is 10³ to 10⁶ times smaller than that required with the conventional direct detection technique in the infra-red. The measuring accuracy and its limiting processes inherent to the infra-red range-resolved differential absorption method are also analysed.     

(TPP)NO3的合成、表征与分子识别NO

在氯仿与无水乙醇的混合溶剂(体积比为1:1)中,四苯基卟啉(TPP)与Ce(NO₃)·6H₂O混合反应后,得产物Ce(TPP)NO₃. 通过紫外-可见光谱、红外光谱、荧光光谱、质谱、核磁共振氢谱的分析与表征,四苯基卟啉与铈原子以四齿方式进行配位,在同一个铈原子上还有一个硝酸根配位. 向Ce(TPP)NO₃的二氯甲烷溶液中通入NO气体,NO可以配位在同一个铈原子上,得到新的配合物Ce(TPP)(NO)NO₃,向此溶液中通入N₂,金属卟啉配合物可以恢复为配合物Ce(TPP)NO₃.     

Remote sensing of mass fluxes of trace gases in the boundary layer

The combination of remote sensing methods like Doppler lidar and FTIR offers the possibility to determine mass fluxes of gases remotely. Doppler lidar measures the three-dimensional wind vector in the vicinity of diffuse sources or the velocity of air in a chimney plume if an industrial complex is monitored. FTIR is a multi-component remote sensing method for gas concentrations. The Fourier transformation of an interferogram of a Michelson interferometer within a FTIR system converts the recorded intensity (function of optical path length) to a spectral signal (function of wavenumber). Both information, velocity and concentration, give the mass fluxes of the tracer (gas). A first test was performed at Munich-North power station with FTIR and cw-Doppler lidar. Fluxes of CO₂, CO, NO, and HC1 were determined. The results are in good agreement with the fluxes measured by in-situ instruments of the power station. The method can be used to control industrial complexes from an outside observation site.     

Synthetic atmospheric transmittance spectra near 15 and 4.3μm

Synthetic monochromatic atmospheric transmittance spectra are presented for infrared intervals in the vicinity of the 15 and 4.3μm CO₂ bands. The intervals are nominally 20 cm^-1 in width, and the spectra partition the intervals [560, 780] cm^-1 and [2180, 2400] cm^-1, respectively. The spectra are for a vertical atmospheric path. A given spectrum is presented at that pressure for which the mean weighting function $\text{(-d}\text{Tau (P)}\text{?d ln P)}$ is a maximum. In order to indicate the molecular origin of the features in a given spectrum, separate spectra are also presented for those species which make center line contributions to the absorption over the interval. The transmittance model for the calculations is described. In addition to the representation of spectral features for intervals which comprise these two CO₂ bands, the spectra afford a utility in the design of high precision satellite temperature radiometers.