机载腔增强吸收光谱系统应用于大气NO_2空间高时间分辨率测量

介绍了一套用于机载平台测量的非相干宽带腔增强吸收光谱(IBBCEAS)系统,并应用于实际大气NO_2空间分布的高时间分辨率观测.为满足机载测量中对时间分辨率的需求,系统采用离轴抛物面镜代替消色差透镜提高光学耦合效率;并运用Allan方差,对系统性能进行了分析.通过腔增强吸收光谱系统与长光程吸收光谱系统对实际大气NO_2的对比测试,两者线性相关系数R~2达到0.86.将IBBCEAS系统应用于机载平台,在时间分辨率为2 s的情况下,探测限达到95 ppt(1σ).通过机载观测,获得了华北地区石家庄等地上空对流层大气NO_2的廓线信息.     

Brillouin spectroscopy in K2Ba(NO2)4

The temperature dependence of elastic stiffnesses of K₂Ba(NO₂)₄ is investigated in the range - 140 to + 160°C, in which two phase transitions have been reported. Marked anomalies appear at the lower transition, in contrast with continuous variations through the upper transition. Results are compared to those obtained near the upper transition by an ultrasonic method and they are qualitatively discussed.     

基于标准样品回归算法和腔增强光谱的NO2检测方法

腔增强吸收光谱技术作为一种高灵敏的痕量气体测量技术,其吸收光谱的浓度反演是极其关键的环节.为消除因吸收截面和仪器响应函数的不确定性引入的测量误差,本文提出了一种基于标准样品吸收光谱的浓度回归算法,该方法在浓度反演过程上进行优化,采用标准气体样品吸收光谱直接拟合未知浓度气体吸收光谱.采用中心波长在440 nm处的蓝色发光二极管(LED)作为光源,建立了一套非相干光腔增强吸收光谱技术(IBBCEAS)系统,实测腔镜反射率为99.915%,利用NO₂气体的实测吸收光谱对该算法的有效性进行了验证.与常规吸收截面回归算法比较,结果表明本文提出的标准样品回归算法具有显著的优越性,测量精度提升约4倍.利用改进的算法结合标准样品配制的多个NO₂气体对实验系统性能进行了深入评估,测量结果与理论值具有很好的一致性.Allan方差分析显示在积分时间为360 s的情况下,NO₂检测限可达到5.3 ppb(1 ppb=10^–9).     

Opto-galvanic spectroscopy of some molecules in discharges: NH2, NO2, H2 and N2

The change of the discharge voltage when laser light crossing the discharge is tuned to a molecular transition has been measured. Experiments have been performed in the wavelength region between 570 nm and 620 nm with discharges in NH₃, NO₂, H₂, N₂, O₂ and argon. Transitions from the ground states of NH₂ and NO₂ and transitions from metastable states of N₂ and H₂ have been detected. The spacial dependence of the opto galvanic in a low pressure dc-discharge of H₂ and N₂ has been studied.     

基于LED光源的非相干宽带腔增强吸收光谱技术探测HONO和NO2

介绍了基于近紫外发光二极管LED (中心波长约372 nm,半高宽13 nm) 光源的非相干宽带腔增强吸收光谱技术,同时用于探测痕量气体HONO和NO₂. LED出射光经准直后耦合进入长度为70 cm,由两块高反射率镜片组成的高精密光学腔内. 分别测量了氮气消光谱和氦气消光谱,通过两者瑞利散射截面的差异而引起光谱强度的变化来标定镜片反射率.在360—390 nm反演波段内,镜片反射率在390 nm处最大且为0.99962, 对应测量NO₂/HONO混合物时的最大光程约1.71 km,并利用最小二乘拟合反演出了 HONO和NO₂的浓度值.当光谱采集时间为1000 s时, HONO和NO₂的探测灵敏度(1σ) 分别为0.6 ppbv和1.9 ppbv.实验结果表明,该技术为实现大气痕量气体的高灵敏度在线监测提供了另一种可能的途径.     

NO2分子高灵敏度痕量探测技术研究

 搭建了一台基于蓝光LED的非相干宽带腔增强吸收光谱系统,并将其应用于NO2分子的高灵敏度痕量探测研究。在3 s采样时间下, 系统探测灵敏度为3.2×10-9 cm-1（1 σ）,对应NO2的探测极限约为187 pmol/mol。利用Allan方差对系统最佳采样时间及系统稳定性进行分析,当采样时间延长至30 s时,系统的探测极限可提高至44 pmol/mol。将该系统应用于实际大气中NO2的连续测量,其测量结果与商业化NOx分析仪（Thermo 42i）进行了比对测试。     

Radiofrequency spectroscopy of AsH3 inside a CO2N2O laser cavity

The method of radiofrequency spectroscopy inside a CO₂N₂O laser cavity has been applied to the observation of pure nuclear quadrupole resonance, A₁-A₂ transitions and two-photon transitions of AsH₃. From the assignment of these transitions some coincidences between laser lines and Δk = 3 transitions in the ν₂ band and Δ|k ? l|; = 3 transitions in the ν₄ band have been assigned. The quadrupole coupling constant eqQ and its rotational dependence χ_J, χ_K and χ_d, and the spin-rotation constants C_N and C_K for the As nucleus have been determined for the ground state. The effective values of eqQ has been determined for the ν₂ and the ν₄ states.     

Infrared laser magnetic resonance (LMR) spectroscopy of NO2 (ν2) with a CO2 laser

The infrared laser magnetic resonance spectra for the ν₂ band of NO₂ were observed by using a CO₂ laser. High-K vibration-rotation transitions from ^rR₆(N) to ^rR₁₁(N) (v₂ = 1 ← 0) were observed. The analysis yielded some molecular parameters including two g factors for the excited vibrational state (v₂ = 1).     

Tunable diode laser spectroscopy of NO2 at 6.2 μm

High-resolution spectra in the ν₃ region of ¹⁴N¹⁶O₂ were measured by using a diode laser as a source to a vacuum grating spectrometer. Spin-rotation constants for the ν₃ and ν₂ + ν₃ states were determined from the observed data. Absolute strengths and transition moments for the ν₃ and ν₂ + ν₃ ? ν₂ bands were derived from the observed line strengths at 296 K. Self-broadened and N₂-broadened half-widths were measured for several of the ν₃ band lines at room temperature. Temperature-dependent half-widths for two N₂-broadened ν₃ lines are also reported.     

Triple quantum MQMAS spectroscopy of (I=7/2) in Na3Co(NO2)6 and trans-Co[(en2)(NO2)2]NO3 interplay between the quadrupole coupling and anisotropic shielding tensors

The purpose of this paper is to investigate the interplay between the chemical shielding anisotropy and quadrupole interaction in MQMAS spectra. in the compounds Na₃Co(NO₂)₆ and trans-Co[(en₂)(NO₂)₂]NO₃ provides model systems for such an investigation. Furthermore, only few results have been reported on the application of the MQMAS method to a spin I=7/2. The possibilities of the MQMAS spectroscopy for determining the relative orientation of the two tensors and its advantage over previous techniques are discussed. Reported experimental spectra at different spinning speeds of Na₃Co(NO₂)₆ are accurately reproduced by our theoretical simulations. The calculations are based on a recent approach, summarized in the present paper, which allows one to perform efficient simulations of MQMAS spectra including all interactions and their time-dependence throughout the experiment. This is necessary for calculating accurate MQMAS spectra including the spinning sideband pattern. In the case of trans-Co[(en₂)(NO₂)₂]NO₃ where the quadrupolar interaction and chemical shielding are stronger and their axes are non-coincident, the MQMAS spectrum is strongly distorted due to the unsufficient spinning speed and RF power. In this case, MAS at different spinning speeds is shown to provide valuable information.     

Uniaxial stress measurements on Rb2PbCu(NO2)6 and K2PbCu(NO2)6

EPR measurements on crystals of compressed tetragonal Rb₂PbCu(NO₂)₆ and K₂PbCu(NO₂)₆ subjected to uniaxial stress have been carried out at various temperatures. The results indicate that uniaxial stress can reorient the crystal axes in both compounds and that smaller stresses are required for Rb₂PbCu(NO₂)₆ than for K₂PbCu(NO₂)₆ at comparable temperatures. Larger stresses are required at lower temperatures.     

Microwave-optical double resonance in NO2

A series of experiments performed to establish the nature of the previously reported microwave optical double resonance signals in electronically excited nitrogen dioxide are reported. The DC stark effect, hyperfine spectrum, and microwave saturation behavior of the double resonance signals observed by exciting NO₂ with the 4880 Å line of an argon ion laser have been studied. The data presented support the assignment of this double resonance signal as occurring within the rovibronic manifold of the ²B₂ electronic state. The observation of a number of new excited state microwave transitions is also reported.     

基于光声光谱技术的NO,NO2气体分析仪研究

NO, NO₂是大气污染源中的常见气体, 对环境具有严重的危害性. 为检测污染源中这两种气体的浓度, 构建了成本较低的基于红外热辐射光源的光声光谱气体检测系统. 分析计算得到了NO, NO₂ 在2500–6667 nm波段吸收谱线. 通过建立光声传输线RLC振荡电路模型和仿真得到品质因数、声压大小与谐振腔长、内腔半径以及调制频率的关系, 据此设计了光声池几何结构. 实验表明该系统所测得的光声信号与气体浓度有很好的线性关系, 并且对NO, NO₂气体极限检测灵敏度分别达到4.01 和1.07 μL. 通过调节激光发射波长和选取滤波片, 该系统还可用于其他微量气体的浓度检测. 关键词： 大气污染 光声光谱 气体检测     

Optical-radio frequency two photon transitions in the double resonance spectrum of NO2

The effect of optical—radio frequency two-photon transitions on the optical—radio frequency double resonance spectrum of NO₂ is investigated.     

Time-resolved site-selection spectroscopy studies of NdAl3(BO3)4 crystals

A pulsed, tunable dye laser was used to selectively excite Nd³⁺ ions in nonequivalent crystal field sites in NdAl₃(BO₃)₄ crystals and energy transfer between ions in different types of sites was studied by monitoring the time evolution of the fluorescence spectrum. The results show that the energy transfer rate varies as t^{$\text{-1}\text{2}$} and increases with temperature. The predictions of various models of phonon-assisted energy transfer are compared to the results.     

Allan variance for optimal signal averaging—monitoring by diode-laser and CO2 laser photo-acoustic spectroscopy

The concept of the Allan variance has been utilized to test the detection abilities of two powerful experimental methods for trace gas monitoring: IR diode-laser and CO₂ laser photo-acoustic spectroscopy. The detection of stable molecules (OCS, allene, CH₃OH), and unstable species (ozone, short-lived free radical CN and molecular ion ArD⁺) have been compared. An approach for studies of the influence of the reactivity on the optimal averaging time for the minimum detectable concentration is demonstrated.     

Time-resolved luminescence of UO2MoO4

Time-resolved spectroscopy and decay-time measurements for the intrinsic and trap emission lines of UO₂MoO₄ supply experimental evidence for fast energy migration among intrinsic centres and from intrinsic to trap centres. The temperature behaviour of the decay time for the main trap lines reveals an energy transfer rate from trap to intrinsic centres in the order of 5×10⁹s^-1, while the transfer rate among intrinsic centres, as estimated from the correlation field splitting, is 3×10¹¹ s^-1.     

Ignition enhancement by addition of NO and NO2 from a N2/O2 plasma torch in a supersonic flow

The effects of NO and NO₂ produced by using a plasma jet (PJ) of a N₂/O₂ mixture on ignition of hydrogen, methane, and ethylene in a supersonic airflow were experimentally and numerically investigated. Numerical analysis of ignition delay time showed that the addition of a small amount of NO or NO₂ drastically reduced ignition delay times of hydrogen and hydrocarbon fuels at a relatively low initial temperature. In particular, NO and NO₂ were more effective than O radicals for ignition of a CH₄/air mixture at 1200 K or lower. These ignition enhancement effects were examined by including the low temperature chemistry. Ignition tests by a N₂/O₂ PJ in a supersonic flow (M = 1.7) for using hydrogen, methane, and ethylene injected downstream of the PJ were conducted. The results showed that the ignitability of the N₂/O₂ PJ is affected by the composition of the feedstock and that pure O₂ is not the optimum condition for downstream fuel injection. This result of ignition tests with downstream fuel injection demonstrated a significant difference in ignition characteristics of the PJ from the ignition tests with upstream fuel injection.     

机载多轴差分吸收光谱技术获取对流层NO2 垂直柱浓度的研究

介绍了一种基于机载平台获取对流层NO₂垂直柱浓度的多轴差分吸收光谱技术. 研究了利用差分吸收光谱技术结合不同观测角度的测量光谱反演差分斜柱浓度, 并利用辐射传输模型SCIATRAN计算对流层NO₂垂直柱浓度的方法. 研究了不同海拔高度、不同地面反照率以及不同太阳天顶角等条件对天顶和天底两个观测角度的大气质量因子的影响. 报道了该系统在2008年12月10日在珠三角地区的实验结果, 结合天顶和天底两个方向反演得到了珠三角地区对流层NO₂垂直柱浓度的分布信息. 同时还将机载测量结果跟安装在珠海市的一台地基多轴差分吸收光谱仪的结果进行了对比, 二者相差仅为8%. 实验结果表明, 机载多轴DOAS技术可以实现对大区域对流层NO₂浓度的快速获取.