光腔衰荡光谱法测量大气中的NO3和N2O5

本文应用基于二极管激光器的双路光腔衰荡光谱技术,分别对大气中NO₃和N₂O₅浓度进行监测. 通过使用实验室标准样校正有效吸收腔长比R_L和系统的总损耗系数?,并获得了NO₃有效吸收截面. 该装置在时间分辨率为1 s时,对NO₃的测量灵敏度达到1.1 pptv,N₂O₅被在线转换成NO₃,从而被另一路光腔衰荡光谱装置探测. 利用该装置,对合肥市区冬季夜间大气中的NO₃,N₂O₅浓度进行了实时监测. 通过对比一次大气快速清洁过程中氮氧化物、臭氧、PM_2.5等组分的浓度变化,讨论了大气环境下可能影响NO₃及N₂O₅浓度的因素.     

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.     

Ni2+ emission in SrF2

Luminescence measurements of X-irradiated SrF₂:Ni are reported. After X-irradiation two emission bands have been found. One of them peaked at 293 nm and has an excitation band at 267 nm. The other one at about 770 nm, which is much weaker, has an excitation band at 274 nm. Both emission bands are also observed under X-ray excitation. A comparison with some previous studies of the absorption and thermoluminescence properties of X-irradiated SrF₂:Ni indicates that the emission bands are due to two different kinds of Ni²⁺ centers. The proposed emission mechanisms are similar to those found in CaF₂:Ni.     

Z-Scan studies of KYW, KYbW, KGW, and Ba(NO3)2 crystals

We present the studies of nonlinear refraction and nonlinear absorption in promising crystals which are extensively used in Raman lasers or as solid-state laser host materials: Ba(NO₃)₂, KGW, KYW, and KYbW. The single-beam z-scan technique with 1 ps laser pulses at 790 and 395 nm has been applied for the study. Nonlinear refraction-index intensity-coefficients and two-photon absorption coefficients have been determined for the crystals. The considerable enhancement of nonlinear refraction is observed in the crystals at 395 nm.     

Interpretation of NO2 absorption in twilight sky spectra

A multiple scattering model has been developed to calculate nitrogen dioxide (NO₂) absorption in the light from the zenith sky during twilight. Model studies show that this absorption is not very sensitive to the atmospheric temperature profile or to tropospheric NO₂.The model was used to interpret some ground-based measurements of NO₂ sky absorption. Values for the total stratospheric column amount vary from 2 to 12×10¹⁵moleccm^-2, and the mean altitude of the stratospheric concentration profile is around 35 km. These observations are in broad agreement with those of other workers.     

Luminescence of Ni doped CaF2

Luminescence measurements of CaF₂ : Ni are reported. Before X-irradiation an emission band at 680 nm is observed with the corresponding excitation band at 255 nm. After RT X-irradiation the emission spectrum consists of three peaks at 290, 375 and 680 nm, all of them with an excitation band at 255 nm. The same emission spectrum together with the electron-hole recombination band is obtained by X-ray excitation.A comparison with previous EPR and optical absorption measurements indicates that the emission bands are due to different kinds of Ni²⁺ centers. The emission processes are similar to those found in CaF₂ : Co and CaF₂ : Mn.     

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.     

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.     

The vacuum ultraviolet spectra of HCN,C2N2, and CH3CN

Quantitative vacuum ultraviolet absorption spectra for HCN, C₂N₂, and CH₃CN have been obtained over the wavelength range 60 nm ? λ ? 160 nm. Where comparison is possible, our measurements of the absorption coefficients for HCN and C₂N₂ are consistent with previous studies. Because of the superior resolution of this work (0.05 nm), vibrational assignments in the valence and Rydberg transitions of HCN have been extended while higher members of the Rydberg series in CH₃CN have been identified.     

用太阳光谱测量空气中NO2浓度的方法研究

根据Noxon方法,利用NO₂在430—450nm范围内的吸收特性,测量空气中NO ₂的浓度.介绍了一种利用光学差分吸收原理,以太阳光为光源,二极管阵列为探测器 ,黄山光明顶上的太阳光谱为参考光谱测量大气中NO₂浓度的新光学方法. 关键词： 太阳光谱 2垂直柱体密度')" href="#">NO₂垂直柱体密度 定日镜 环境空气质量监测     

Photoacoustic detection of NO2 traces with CW and pulsed green lasers

Photoacoustic NO₂ traces detection based on continuous and pulsed lasers emitting at 532 nm is presented. Both systems were calibrated with known NO₂-pure air mixtures. A minimum detectable volume concentration of 20 parts in 10⁹ (S/N=1) and 15 parts in 10⁹ for the resonant and pulsed regime, respectively, were obtained. These values were limited by electrical and acoustical noise of the microphone and electronics. Measurements of NO₂ concentrations in urban air are compared with home-manufactured mixtures. Traces of nitrogen dioxide from two different car exhausts are also detected and quantitatively assigned from the calibration curves.     

Water vapor differential absorption lidar measurements using a diode-pumped all-solid-state laser at 935 nm

A diode-pumped, single-frequency laser system emitting at 935 nm has recently been developed to serve as the transmitter for water vapor differential absorption lidar (DIAL) measurements. This laser uses Nd:YGG (Y₃Ga₅O₁₂) as the active medium and emits radiation directly at 935 nm without the need of additional frequency conversion processes. The system was diode-pumped at 806 nm and was built up in a master-oscillator-power-amplifier configuration. It generates more than 30 mJ of pulse energy at 100 Hz repetition rate with a beam quality (M ²) of better than 1.4. Since water vapor DIAL demands for stringent requirements of the spectral properties those were carefully investigated in the scope of this paper. Single-frequency operation is achieved by injection seeding and active length control of the oscillator cavity. The range of continuously tunable single-frequency radiation extends to ～0.4 nm centered around 935.31 nm. Values of the spectral purity of >99.996% were determined using long-pass absorption measurements in the atmosphere exceeding the requirements by a large margin. Finally, for the first time water vapor DIAL measurements were performed using a Nd:YGG laser. The reported results show much promise of these directly pumped lasers at 935 nm for future spaceborne but also airborne water vapor lidar systems.     

多孔TiO2/Al/SiO2纳米复合结构的紫外光吸收特性研究

在SiO₂玻璃衬底上用脉冲激光沉积(PLD)技术，分别沉积Ti和Ti/Al膜，经电化学阳极氧化成功制备了多孔TiO₂/SiO₂和TiO₂/Al/SiO₂纳米复合结构. 其中TiO₂薄膜上的微孔阵列高度有序，分布均匀. 实验研究了Al过渡层对多孔TiO₂薄膜光吸收特性的影响. 结果表明：无Al过渡层的多孔TiO₂薄膜其紫外吸收峰在27     

多孔TiO2/Al/SiO2纳米复合结构的紫外光吸收特性研究

在SiO₂玻璃衬底上用脉冲激光沉积(PLD)技术,分别沉积Ti和Ti/Al膜,经电化学阳极氧化成功制备了多孔TiO₂/SiO₂和TiO₂/Al/SiO₂纳米复合结构. 其中TiO₂薄膜上的微孔阵列高度有序,分布均匀. 实验研究了Al过渡层对多孔TiO₂薄膜光吸收特性的影响. 结果表明：无Al过渡层的多孔TiO₂薄膜其紫外吸收峰在27 关键词： 2薄膜')" href="#">多孔TiO₂薄膜 阳极氧化 紫外光吸收     

Development of an open-path incoherent broadband cavity-enhanced spectroscopy based instrument for simultaneous measurement of HONO and NO2 in ambient air

We report on the development of an optical instrument based on incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) for simultaneous open-path measurements of nitrous acid (HONO) and nitrogen dioxide (NO₂) in ambient air using a UV light emitting diode operating at ∼366 nm. Detection limits of ∼430 pptv for HONO and ∼1 ppbv for NO₂ were achieved with an optimum acquisition time of 90 s, determined by an Allan variance analysis. Based on a 1.85 m long high optical finesse open-path cavity, the effective optical path length of 2.8 km was realized in aerosol-free samples or in an urban environment at modest aerosol levels. Such a kilometer long optical absorption is comparable to that achieved in the well established differential optical absorption spectroscopy (DOAS) technology while keeping the instrument very compact. Open-path detection configuration allows one to avoid absorption cell wall losses and sampling induced artifacts. The demonstrated sensitivity and specificity shows high potential of this cost-effective and compact infrastructure for future field applications with high spatial resolution.     

ATMOSPHERIC REMOTE-SENSING REFERENCE DATA FROM GOME: PART 1. TEMPERATURE-DEPENDENT ABSORPTION CROSS-SECTIONS OF NO2 IN THE 231–794 nm RANGE

Absorption cross-sections of NO₂ between 231–794 nm have been measured in the 221–293 K temperature range, using the global ozone monitoring experiment (GOME) flight-model (FM) satellite spectrometer. The spectra have a resolution of about 0.2 nm below 400 nm and of about 0.3 nm above 400 nm. These are the first reference spectra of NO₂ covering at the same time the entire UV–visible–NIR spectral range and a broad range of relevant atmospheric temperatures. The new absorption cross-sections are important as accurate reference data for atmospheric remote-sensing of NO₂ and other minor trace gases.     

Aerosol influence on polarization and intensity in near-infrared O2 and CO2 absorption bands observed from space

We study the intensity and degree of linear polarization of reflected solar radiation at the top of the atmosphere within two carbon dioxide bands and one oxygen absorption band in the near-infrared. In particular, we are interested in the sensitivity of the degree of linear polarization and intensity to changes of aerosol and cirrus cloud layer heights, microphysical properties, and surface albedo. For the simulations we use spectral response functions representative of the Orbiting Carbon Observatory (OCO). Inside the O₂A band at 760 nm and strong CO₂ band at 2060 nm we find a strong influence of the aerosol and cirrus cloud layer height on the degree of linear polarization. An increase of the aerosol or cirrus cloud layer height can lead either to a decrease or increase of the polarization within the band, depending on the microphysical and optical properties of the scatterers, surface albedo, and absorption strength in the bands. The results for the O₂A band also indicate that even over land OCO enables an estimation of the height of an aerosol or cirrus cloud layer. Inside the weak CO₂ band at 1610 nm the influence of aerosol or cirrus cloud layer heights is lower as compared to the O₂A band and CO₂ band at 2060 nm, due to the relatively stronger surface influence. Here an increase of aerosol or cirrus cloud layer height leads to an increase of the degree of linear polarization even in case of low surface albedo and for weakly polarizing scatterers. For the weak CO₂ band at 1610 nm we also study the influence of the aerosol or cirrus cloud layer height on the column CO₂ estimate and the errors resulting from ignoring polarization in simulations of backscatter measurements by space-based instruments such as OCO. Depending on the surface albedo, misinterpretations of the height of atmospheric scatterers might strongly affect the column CO₂ estimates.     

Synthesis and nonlinear optical characterization of SnO2 quantum dots

The present paper demonstrates the preparation and characterization of SnO₂ semiconductor quantum dots. Extremely small ∼1.1 and ∼1.4 nm SnO₂ samples were prepared by microwave assisted technique with a frequency of 2450 MHz. Based on XRD analysis, the phase, crystal structure and purity of the SnO₂ samples are determined. UV-vis measurements showed that, for the both size of SnO₂ samples, excitonic peaks are obtained at ∼238 and ∼245 nm corresponding to ∼1.1 nm (sample 1) and ∼1.4 nm (sample 2) sizes, respectively. STM analysis showed that, the quantum dots are spherical shaped and highly monodispersed. At first, the linear absorption coefficients for two different sizes of SnO₂ quantum dots were measured by employing a CW He-Ne laser at 632.8 nm and were obtained about 1.385 and 4.175 cm⁻¹, respectively. Furthermore, the nonlinear refractive index, n₂, and nonlinear absorption coefficient, β, were measured using close and open aperture Z-scan respectively using the same laser. As quantum dots have strong absorption coefficient to obtain purely effective n₂, we divided the closed aperture transmittance by the corresponding open aperture in the same incident beam intensity. The nonlinear refraction indices of these quantum dots were measured in order of 10⁻⁷ (cm²/W) with negative sign and the nonlinear absorption coefficients were obtained for both in order of 10⁻³ (cm/W) with positive sign.     

Excited-state absorption of Co2+ in MgF2 and KZnF3

We report on measurements of excited-state absorption spectra and absolute cross-sections in Co²⁺-doped KZnF₃ and MgF₂ at room temperature in the near-infrared domain. The data are compared with the predictions of the single-configuration co-ordinate model.     

Electrical conductivity and dielectric loss in doped Pb(NO3)2 single crystals

dc ionic conductivity measurements were made on single crystals of Pb(NO₃)₂ doped with monovalent Na⁺ and K⁺ in the temperature range of 100–400°C. In the extrinsic region the conductivity was found to decrease with Na⁺ having a smaller ionic size, and to increase with K⁺ with larger ionic size compared to the host Pb ion. Conductivity is attributed to the mobility of anti-Frenkel defects as in the case of PbF₂. Dielectric loss measurements were made on the Pb(NO₃)₂: K⁺ system in the frequency range of 300 Hz to 20 kHz at different temperatures. Impurity vacancy pairs of the type K⁺-(NO^-₃)_V are found to be responsible for the observed dielectric loss peaks. The maximum peak frequency is found to increase with temperature.