Measurement of tropospheric CO2 and aerosol extinction profiles with Raman lidar

A prototype Raman lidar was designed for monitoring tropospheric CO2 profile and other scientific investigatious.The third harmonic of Nd:YAG laser (354.7-nm wavelength) was used as stimulated light source to provide nighttime measurements.Filter with high rejection ratio performance was used to extract CO2 Raman signals from Rayleigh-Mie scattering signals effectively.To improve the real time monitoring function,a two-channel signal collection system was designed to collect CO2 and N2 Raman scattering signals simultaneously. The N2 Raman scattering signals were used to retrieve aerosol extinction coefficient.Typical features of CO2 concentration profile and aerosol extinction coefficient in Herei were presented.The mixing ratio of atmospheric CO2 in Hefei can reach about 360-400 ppmv.     

多波长激光雷达探测多种天气气溶胶光学特性与分析

设计和构建了波长为355,532和1064nm的多波长米散射激光雷达系统,并研究了多波长激光雷达信号数据处理和反演算法,实现了对地表气溶胶的探测;利用该激光雷达对2013年冬季西安市上空大气进行了探测,研究分析了雾霾天、晴天和有云天气的混合层高度、气溶胶消光特征和粒径分布特征.分析比较了不同波长探测到的混合层高度变化情况.在雾霾天,大气混合层高度与晴天和有云天相比明显偏低,在0.4 km附近,而晴天的混合层高度有0.5—0.8 km.利用长波(1064 nm/532 nm)段和短波(532 nm/355 nm)段两个ngstrm指数分析了不同天气情况下的粒径分布特征.对于近地层气溶胶,雾霾天的长波ngstrm(1064/532)指数小于短波ngstrm(532/355)指数,而晴天与之相反,说明在近地层雾霾有污染的大气中,存在有较多的粗粒子.在云层中,ngstrm指数明显减小,并且出现负值,说明云粒子半径比较大.     

Simultaneous detection of SO2, SO3 and H2O using QCL spectrometer for combustion applications

We demonstrate a high-sensitivity laser-based spectrometer for simultaneous detection of sulphur dioxide (SO₂) sulphur trioxide (SO₃) and water for coal-fired combustion applications. The spectrometer is based on a quantum-cascade laser (QCL) operating at 7.16 μm, capable of measuring all three components simultaneously in a single frequency sweep. An optical multipass cell having a total path length of 9.1 m is used at increased temperature and at low pressure to ensure reliable measurement of highly reactive SO₃ and adequate separation of overlapping spectral features, respectively. Detection limits for SO₂ and SO₃ are 0.134 and 0.0073 ppm, respectively, when employing a 20-s sampling time.     

Radiative electron-attachment spectra of O3 and SO2

Several aspects of radiative electron-attachment processes are discussed and the corresponding photon energy spectra computed for O₃ and SO₂. In both cases the vibrational stretching mode is significantly excited. The calculated electron attachment spectrum of SO₂ is compared with the laser photo-detachment spectrum of SO₂ ^-. The computed electron affinities and changes in geometry between natural and negative ion are in good agreement with the experimental data.     

Ion secondary electron emission from Al2O3 and MgO films

Coefficients of ion induced secondary electron emission (ISEE) γ from thin films of Al₂O₃ and MgO have been measured for argon ions in the energy range between 0–3 keV. Dionne's equation for secondary electron emission, which consists of production and emission terms has been modified to explain the kinetic emission of ISEE. The production term for ion induced secondary electrons has been separately formulated, taking account of the energy loss of primary ions, while the process of emission is considered to remain the same as in SEE. The escape depth λ_S and emission probability B were obtained from the SEE data and were used, along the range value of incident ions, to calculate the emission term in ISEE. The modified form of the equation was used to evaluate theoretically expected ISEE yield energy curves. Fairly good correlation is observed in theoretical and experimental curves which supports the validity of the proposed theoretical model.     

O− emission from 12CaO·7Al2O3 and MSZ composite and its application for silicon oxidation

The solid electrolyte 12CaO·7Al₂O₃ (C12A7) is an interesting material where an atomic oxygen radical anion (O⁻) can be emitted from the C12A7 to vacuum when it is heated to 1000 K under an applied electric field (100 V/cm). However, the mechanical strength of the C12A7 is not enough for an application study. In order to enhance the mechanical strength of the C12A7, a magnesia-stabilized zirconia (MSZ) support C12A7 film composite was developed, and ion emission from the MSZ/C12A7 composite was investigated. The MSZ/C12A7 composite showed O⁻ emission and also electron emission. The generated O⁻ was applied to a silicon sample to confirm its oxidation ability. Even though the surface temperature is less than 383 K, SiO₂ film formation was achieved.This O⁻ oxidation method is applicable for low-temperature and low-damage silicon oxidation processes.     

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.     

XPS and auger spectroscopy studies on mixtures of the oxides SiO2, Al2O3, Fe2O3 and Cr2O3

X-ray photoelectron Spectroscopy (XPS) and X-ray-induced Auger Spectroscopy were utilized to examine qualitative and quantitative aspects involved in the surface analysis of mechanical mixtures of the title oxides. Consideration of O1s and OKVV bands of the mixtures makes it possible to distinguish between the single oxide components. The energy shift between the Fe₂O₃ and SiO₂ (or Al₂O₃) components is about twice as large in the OKVV region as in the O1s region. By way of contrast, Auger Spectroscopy analysis of the mixtures does not appear to enable a quantitative distinction between the constituent oxides to be made. Conversely, XPS analysis provides instead quantitative results, although these are affected by a relative error of ± 10%. A simple approach, based on intensity ratio measurements of the single O1s components, enables relatively accurate quantitative results to be obtained.It is shown that analysis of appropriate mixtures is a useful case study for investigations on surface and interface properties of real materials. Argon ion etching effects on the mixtures and on the title oxides analyzed separately are reported.     

Raman spectra of mirabilite,Na2SO4·10H2O and the rediscovered metastable heptahydrate,Na2SO4·7H2O

Salt crystallisation in pores is known to cause serious damage to masonry. Sodium sulphate, often regarded as one of the most damaging salts, has a rich hydrate chemistry including one rediscovered metastable hydrate and a new high pressure octahydrate plus five known polymorphs of the anhydrous phase. The difficulty in working with these hydrates lies in their strong tendency to dehydrate or to convert to the stable phase, in the case of the heptahydrate. We present Raman spectra and a table of peak wavenumbers for randomly oriented crystals of mirabilite and the metastable heptahydrate, sufficient to distinguish between these phases that have SO₄ν₁ values of 989.3 and 987.6 cm⁻¹, respectively. Mirabilite has a Raman spectrum very similar to the free sulphate anion in solution, which is probably due to the mobility of oxygen atoms within the sulphate tetrahedron. The oxygen atoms in the heptahydrate sulphate groups have no partial occupancy, and predicted peak splitting is observed in the region 400–1200 cm⁻¹. Copyright © 2010 John Wiley & Sons, Ltd.     

ICP-AES同时测定铬质引流剂中的Cr2O3、Al2O3、Fe2O3和MgO

探讨了电感耦合等离子体-原子发射光谱法(ICP-AES)测定铬质引流剂中Cr2O3、Al2O3、Fe2O3和MgO的分析条件.试样经过氧化钠熔融分解,盐酸酸化,采用内标加入法,利用ICP光谱仪于所推荐的波长处,测量溶液中铬、铝、铁、镁元素对钇内标元素的相对强度,根据标准溶液绘制的校准曲线计算出待测元素氧化物的质量分数.对该方法进行精密度试验,相对标准偏差(RSD,n=8)均小于1.0％,本测试方法简单、快速、精度高,将该方法用于铬质引流剂中Cr2O3、Al2O3、Fe2O3和MgO含量的测定,取得满意效果.     

Excited state absorption and stimulated emission of Nd3+ in crystals. Part I: Y3Al5O12, YAlO3, and Y2O3

4 F_3/2 excited state of the Nd³⁺ ion in Y₃Al₅O₁₂, YAlO₃, and Y₂O₃ were measured in a continuous wave pump- and probe experiment in a wide spectral range from 850 nm (780 nm for Y₃Al₅O₁₂) to 1500 nm. The cross sections were determined from a comparison with the emission spectra and the simultaneously measured ground state absorption bleaching. The strongest excited state absorption transitions were found in the 1220–1400 nm spectral region due to transitions to the ²G_9/2 and ⁴G_7/2 levels. The spectral positions of the measured transitions are in good agreement with the theoretically expected transitions calculated from the known Stark-level splittings. Received: 4 December 1997/Revised version: 8 May 1998     

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.     

Growth of Bi2O3 rods using a trimethylbismuth and oxygen mixture

We have successfully grown the rod-like structures of bismuth oxide (Bi₂O₃) on silicon substrate by a reaction of a trimethylbismuth (TMBi) and oxygen (O₂) mixture without using any catalyst. We have characterized the samples by means of X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The products consisted of bundles of rod-like structures. The Bi₂O₃ rods were of monoclinic structure. PACS 81.07.-b; 81.15.Gh     

Space-borne remote sensing of CO2, CH4, and N2O by integrated path differential absorption lidar: a sensitivity analysis

CO₂, CH₄, and N₂O are recognised as the most important greenhouse gases, the concentrations of which increase rapidly through human activities. Space-borne integrated path differential absorption lidar allows global observations at day and night over land and water surfaces in all climates. In this study we investigate potential sources of measurement errors and compare them with the scientific requirements. Our simulations reveal that moderate-size instruments in terms of telescope aperture (0.5–1.5 m) and laser average power (0.4–4 W) potentially have a low random error of the greenhouse gas column which is 0.2% for CO₂ and 0.4% for CH₄ for soundings at 1.6 μm, 0.4% for CO₂ at 2.1 μm, 0.6% for CH₄ at 2.3 μm, and 0.3% for N₂O at 3.9 μm. Coherent detection instruments are generally limited by speckle noise, while direct detection instruments suffer from high detector noise using current technology. The wavelength selection in the vicinity of the absorption line is critical as it controls the height region of highest sensitivity, the temperature cross-sensitivity, and the demands on frequency stability. For CO₂, an error budget of 0.08% is derived from our analysis of the sources of systematic errors. Among them, the frequency stability of ± 0.3 MHz for the laser transmitter and spectral purity of 99.9% in conjunction with a narrow-band spectral filter of 1 GHz (FWHM) are identified to be challenging instrument requirements for a direct detection CO₂ system operating at 1.6 μm. PACS 42.68.Wt; 95.75.Qr     

Search for new transparent conductors: Effect of Ge doping on the conductivity of Ga2O3, In2O3 and Ga1.4In0.6O3

Only a small amount (≤3.5 mol%) of Ge can be doped in Ga₂O₃, Ga_1.4In_0.6O₃ and In₂O₃ by means of solid state reactions at 1400 °C. All these samples are optically transparent in the visible range, but Ge-doped Ga₂O₃ and Ga_1.4In_0.6O₃ are insulating. Only Ge-doped In₂O₃ exhibits a significant decrease in resistivity, the resistivity decreasing further on thermal quenching and H₂ reduction. The resistivity of 2.7% Ge-doped In₂O₃ after H₂ reduction shows a metallic behavior, and a resistivity of ～1 mΩ cm at room temperature, comparable to that of Sn-doped In₂O₃.     

Effect of a single water molecule on the formations of H2O2 + ClO from HO2 + HOCl reaction under tropospheric conditions

ABSTRACT

In this work, four different channels, represented by H₂O???HO₂ + HOCl, HO₂???H₂O + HOCl, H₂O???HOCl + HO₂ and HOCl???H₂O + HO₂ have been analysed for water-catalysed formations of H₂O₂ + ClO to gain insight into the potential impact of the reaction in the atmosphere. The results at the CCSD(T)/aug-cc-pVTZ//MP2/6-311+G(2df,2p) level show that the H₂O???HO₂ + HOCl reaction is kinetically the most favourable channel among the four channels. Compared to the channel of H₂O₂ + ClO formations without water vapour, the effective rate constant of H₂O???HO₂ + HOCl reaction is estimated to be faster than the naked reaction by 2–3 orders of magnitude, indicating that the single water molecule in the H₂O???HO₂ + HOCl channel exhibits a positive catalytic effect on enhancing the rate of H₂O₂ + ClO formations. Meanwhile, it is interesting that the transfer process between H₂O???HOCl + HO₂ and H₂O???HO₂ + HOCl has an activation energy of 0.6 kcal?mol^?1 and can occur easily under tropospheric conditions.     

光谱纯Y2O3,La2O3,Lu2O3中微量杂质的光致发光谱研究

测定了光谱纯稀土化合物Ｙ２Ｏ３，Ｌａ２Ｏ３，Ｌｕ２Ｏ３中微量杂质在４８８．０ｎｍ和５１４．５ｎｍ激光线激发下的光致发光谱以及在可见光４４５～７４１ｎｍ范围内吸收谱，Ｙ２Ｏ３，Ｌｕ２Ｏ３样品在４４８．０ｎｍ和５１４．５ｎｍ激光激发下都有发光效应，而Ｌａ２Ｏ３样品只在４８８．０ｎｍ激光激发下才发光，分析了结果表明，Ｙ２Ｏ３，Ｌａ２Ｏ３，Ｌｕ２Ｏ３的发光谱分别是由其存在的微量Ｅｒ＾３＋，Ｓｍ＾３＋和Ｅｕ     

Optical and scintillation properties of Sc2O3, Y2O3 and Lu2O3 transparent ceramics synthesized by SPS method

Sc₂O₃, Y₂O₃ and Lu₂O₃ transparent ceramics were prepared by the spark plasma sintering (SPS) method. After polishing, the samples were semitransparent. Their optical transmittance was 10–40% at 500 nm which corresponded with their semi-transparency. In the X-ray induced emission spectra, a broad emission peak appeared around 335 nm in each sample. For this wavelength, scintillation decay time for Y₂O₃ and Sc₂O₃ were 22 and 48 ns, respectively. The light yield of Sc₂O₃, Y₂O₃ and Lu₂O₃ was 16,200, 2600, and 200 ph/5.5 MeV-alpha, respectively, which followed from the alpha-ray induced pulse height spectra. The gamma-ray induced light yield of Sc₂O₃ was 11,500 ph/MeV, which is 1.4 times larger than that of conventional single crystal BGO (Bi₄Ge₃O₁₂) scintillator. Light yield non-proportionality and energy resolution of Sc₂O₃ were examined for the first time.