On-line multicomponent trace-gas analysis with a broadly tunable pulsed difference-frequency laser spectrometer

The design and application of a novel automated room-temperature laser spectrometer are reported. The compact instrument is based on difference-frequency generation in bulk LiNbO(3). The instrument employs a tunable cw external-cavity diode laser (795-825 nm) and a pulsed diode-pumped Nd:YAG laser (1064 nm). The generated mid-IR nanosecond pulses of 50-muW peak power and 6.5-kHz repetition rate, continuously tunable from 3.16 to 3.67 mum, are coupled into a 36-m multipass cell for spectroscopic studies. On-line measurements of methane are performed at concentrations between 200 ppb (parts in 10(9) by mole fraction) and approximately 1%, demonstrating a large dynamic range of 7 orders of magnitude. Furthermore computer-controlled multicomponent analysis of a mixture containing five trace gases and water vapor with an overall response time of 90 s at an averaging time of only approximately 30 s is reported. A minimum detectable absorption coefficient of 1.1 x 10(-7) cm(-1) has been achieved in an averaging time of 60 s, enabling detection limits in the ppb range for many important trace gases, such as CH(4), C(2)H(6), H(2)CO, NO(2), N(2)O, HCl, HBr, CO, and OCS.     

FOX-7在炸药中的应用述评

FOX-7是一种性能优异的不敏感单质炸药,也是今后在低易损弹药上推广应用的主要候选炸药之一。重点综述了国内外近年来报道的FOX-7在炸药中的应用及性能研究进展,包括FOX-7的合成制备、分子结构及晶型、表界面性能、热安定性能以及以FOX-7为基的炸药的机械感度、爆速、爆压、冲击波感度、小尺寸装药快速烤燃、慢速烤燃、子弹撞击试验等。其中,对FOX-7炸药不敏感性的评价方式主要是与相同状态的RDX基炸药和TNT炸药进行试验对比。指出FOX-7是一种具有应用价值的高能不敏感炸药,要实现FOX-7炸药在弹药中的应用,今后还要加强高品质、规模化、低成本FOX-7制备工艺技术研究以及FOX-7炸药在大尺寸战斗部中的装药技术研究。     

Real-time quantification of traces of biogenic volatile selenium compounds in humid air by selected ion flow tube mass spectrometry

Biological volatilization of selenium, Se, in a contaminated area is an economical and environmentally friendly approach to phytoremediation techniques, but analytical methods for monitoring and studying volatile compounds released in the process of phytovolatilization are currently limited in their performance. Thus, a new method for real time quantification of trace amounts of the vapors of hydrogen selenide (H(2)Se), methylselenol (CH(3)SeH), dimethylselenide ((CH(3))(2)Se), and dimethyldiselenide ((CH(3))(2)Se(2)) present in ambient air adjacent to living plants has been developed. This involves the characterization of the mechanism and kinetics of the reaction of H(3)O(+), NO(+), and O(2)(+?) reagent ions with molecules of these compounds and then use of the rate constants so obtained to determine their absolute concentrations in air by selected ion flow tube mass spectrometry, SIFT-MS. The results of experiments demonstrating this method on emissions from maize (Zea mays) seedlings cultivated in Se rich medium are also presented.     

Photoacoustic spectroscopy on trace gases with continuously tunable CO(2) laser

A novel photoacoustic (PA) system that uses a continuously tunable high-pressure CO(2) laser as radiation source is presented. A minimum detectable absorption coefficient of 10(-6) cm(-1) that is limited mainly by the desorption of absorbing species from the cell walls and by residual electromagnetic perturbation of the microphone electronics has currently been achieved. Although a linear dependence of the PA signal on the gas concentration has been observed over 4 orders of magnitude, the dependence on energy exhibits a nonlinear behavior owing to saturation effects in excellent agreement with a theoretical model. The calibration of the laser wavelength is performed by PA measurements on low-pressure CO(2) gas, resulting in an absolute accuracy of ± 10(-2) cm(-1). PA spectra are presented for carbon dioxide (CO(2)), ammonia (NH(3)), ozone (O(3)), ethylene (C(2)H(4)), methanol (CH(3)OH), ethanol (C(2)H(5)OH), and toluene (C(7)H(8)) in large parts of the laser emission range. The expected improvement in detection selectivity compared with that of studies with line-tunable CO(2) lasers is demonstrated with the aid of multicomponent trace-gas mixtures prepared with a gas-mixing unit. Good agreement is obtained between the known concentrations and the concentrations calculated on the basis of a fit with calibration spectra. Finally, the perspectives of the system concerning air analyses are discussed.     

Thermal behavior, specific heat capacity and adiabatic time-to-explosion of G(FOX-7)

[H(2)NC(NH(2))(2)](+)(FOX-7)(-)-G(FOX-7) was prepared by mixing FOX-7 and guanidinium chloride solution in potassium hydroxide solution. Its thermal decomposition was studied under the non-isothermal conditions with DSC and TG/DTG methods. The apparent activation energy (E) and pre-exponential constant (A) of the two exothermic decomposition stages were obtained by Kissinger's method and Ozawa's method, respectively. The critical temperature of thermal explosion (T(b)) was obtained as 201.72 degrees C. The specific heat capacity of G(FOX-7) was determined with Micro-DSC method and theoretical calculation method and the standard molar specific heat capacity is 282.025Jmol(-1)K(-1) at 298.15K. Adiabatic time-to-explosion of G(FOX-7) was also calculated to be a certain value between 13.95 and 15.66s.     

Quantitative analysis of liquids from aerosols and microdrops using laser induced breakdown spectroscopy

Laser induced breakdown spectroscopy (LIBS) is shown to be capable of low volume (90 pL) quantitative elemental analysis of picogram amounts of dissolved metals in solutions. Single-pulse and collinear double-pulse LIBS were investigated using a 532 nm dual head laser coupled to a spectrometer with an intensified charge coupled device (CCD) detector. Aerosols were produced using a micronebulizer, conditioned inside a concentric spray chamber, and released through an injector tube with a diameter of 1 mm such that a LIBS plasma could be formed ~2 mm from the exit of the tube. The emissions from both the aerosols and a single microdrop were then collected with a broadband high resolution spectrometer. Multielement calibration solutions were prepared, and continuing calibration verification (CCV) standards were analyzed for both aerosol and microdrop systems to calculate the precision, accuracy, and limits of detection for each system. The calibration curves produced correlation coefficients with R(2) values > 0.99 for both systems. The precision, accuracy, and limit of detection (LOD) determined for aerosol LIBS were averaged and determined for the emission lines of Sr II (421.55 nm), Mg II (279.80 nm), Ba II (493.41 nm), and Ca II (396.84 nm) to be ~3.8% RSD, 3.1% bias, 0.7 μg/mL, respectively. A microdrop dispenser was used to deliver single drops containing 90 pL into the space where a LIBS plasma was generated with a focused laser pulse. In the single drop microdrop LIBS experiment, the analysis of a single drop, containing a total mass of 45 pg, resulted in a precision of 13% RSD and a bias of 1% for the Al I (394.40 nm) emission line. The absolute limits of detection of single drop microdrop LIBS for the emission lines Al I (394.40 nm) and Sr II (421.5 nm) were approximately 1 pg, and Ba II (493.41 nm) produced an absolute detection limit of approximately 3 pg. Overall, the precision, accuracy, and absolute LOD determined for single microdrop LIBS resulted in a typical performance of ~14% RSD, 6% bias, and 1 pg for the elements Sr II (421.55 nm), Al I(394.40 nm), Mg II (279.80), and Ba II(493.41 nm).     

Quantitative analysis of toxic metals lead and cadmium in water jet by laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) has been applied to the analysis of toxic metals Pb and Cd in Pb(NO3)2 and Cd(NO3)2.4H2O aqueous solutions, respectively. The plasma is generated by focusing a nanosecond Nd:YAG (λ=1064?nm) laser on the surface of liquid in the homemade liquid jet configuration. With an assumption of local thermodynamic equilibrium (LTE), calibration curves of Pb and Cd were obtained at different delay times between 1 to 5?μs. The temporal behavior of limit of detections (LOD) was investigated and it is shown that the minimum LODs for Pb and Cd are 4 and 68 parts in 10(6) (ppm), respectively. In order to demonstrate the correctness of the LTE assumption, plasma parameters including plasma temperature and electron density are evaluated, and it is shown that the LTE condition is satisfied at all delay times.     

Short-wavelength near-infrared spectra of sucrose, glucose, and fructose with respect to sugar concentration and temperature

Short-wavelength near-infrared (SW-NIR) (700-1100 nm) spectra of aqueous solutions of sucrose, D-glucose, and D-fructose were monitored with respect to change in temperature and sugar concentration. Sugar OH and CH related vibrations were identified by analysis of the spectra of sugar solutions in deuterium oxide (D2O), and of sucrose-d8 solutions in D2O. Absorption spectra were explained in terms of the second and third overtones of OH stretching vibrations and the third overtone of CH2 and CH stretchings. In deuterated solutions, CH and CH2 higher overtone vibration bands became apparent. The major spectral effect of decreased temperature or increased sugar concentration was a decrease in absorbance at 960 nm and an increase in absorbance at 984 nm, interpreted as an increase in the degree of H bonding. Partial least-squares (PLS) calibrations on sugar concentrations (with spectra collected at several sample temperatures) relied strongly on the 910 nm sugar CH related bands, whereas calibrations on temperature depended equally on all OH associated vibrations (750, 840, 960, and 985 nm).     

Raman spectroscopic investigation of solid samples using a low-repetition-rate pulsed Nd:YAG laser as the excitation source

We tried to investigate the possibility of using a low-repetition-rate pulsed Nd:YAG laser as an excitation source in Raman measurements for solid samples. Based on the results from the Raman spectra excited by continuous wave (CW) 532 and 325 nm lasers, we studied the influence of laser energy and irradiation time of 532 and 355 nm pulsed Nd:YAG lasers (10 Hz repetition rate) on the thermal stability of (NH4)6Mo7O(24).4H2O, NH4VO3, and Ce(NO3)(3).6H2O samples, which usually decompose at relatively low temperatures. It is observed that the heating temperature estimated at these samples caused by the irradiation of 532 nm pulsed laser with 22 mJ is no higher than 100 degrees C even for 60 min exposure. The 355 nm pulsed laser with energies below 8.0 mJ hardly causes thermal damage to hydrated (NH4)6Mo7O24 and hydrated Ce(NO3)3 SAMPLES: However, a 355 nm pulsed laser with only 2.2 mJ causes heating temperatures as high as 200 degrees C in the NH4VO3 SAMPLE: These great differences should be attributed to the electronic absorbance of the above three samples at 355 nm. We also found that a 532 nm pulsed laser with even 22 mJ and a 355 nm pulsed laser with even 8.0 mJ do not cause the phase transition of TiO2 and ZrO2, whose phase transformation easily takes place at elevated temperatures, but pulsed lasers could remove some oxygen atoms from these samples. In addition, for L-alanine and DL-beta-phenylalanine biological samples, it is surprisingly found that they are not damaged by the 355 nm pulsed laser even when the laser energy is increased to 8.0 mJ, possibly because they do not absorb the 355 nm laser. Based on these results, it is demonstrated that low-repetition-rate pulsed lasers with appropriate wavelength and energy can be employed as the excitation sources of Raman spectroscopy for characterizing some solid samples, even the thermally unstable samples.     

FOX-7与RDX混合比例对压装炸药慢速烤燃及冲击波感度的影响

利用慢速烤燃试验和冲击波感度试验研究了FOX-7与 RDX不同混合比例对炸药响应特性的影响。试验表明:当FOX-7的混入量（质量分数）低于72%时，炸药在慢速烤燃试验中的响应剧烈程度表现为爆轰反应，其临界起爆压力接近6.62 GPa；当FOX-7的混入量（质量分数）等于72%时，炸药在慢速烤燃试验中的响应剧烈程度由爆轰降至爆燃，其临界起爆压力升至7.27 GPa；当配方中完全采用FOX-7时，炸药在慢速烤燃试验中的响应剧烈程度由爆燃降至燃烧，临界起爆压力升至8.24 GPa。造成上述试验结果的原因可能是压装炸药在成型过程中因颗粒的破碎、重排作用使FOX-7对RDX形成包覆，进而改善了RDX材料点火增长速度快的本质特点。     

钕掺杂Ti／TiO2电极的制备并用于油田废水的降解实验研究

以Ti（OBu）4、二乙醇胺、C2H3OH、Nd（NO3）,为前驱体,制备稀土（Nd）掺杂TiO22溶胶,以钛电极为基体,用溶胶-凝胶法制备稀土（Nd）掺杂TiO2电极,优化了制备改性研O2电极的稀土掺杂量、热处理温度及热处理时间。以油田废水为目标有机物,借助于COD去除情况分析电极的电催化氧化能力;分析了电极结构与电催化特性之间的关系。采用SEM、EDX和XRD分析了制备电极的表面形貌、元素组成、晶体结构。掺杂Nd后电极的表面凹凸感变小,表面更为平滑、致密,几乎没有裂缝,这种均匀一致的高密度小碎片结构可能具有较大的表面粗糙度和比表面积,有利于催化反应。TiO2电极的晶体结构主要为锐钛矿型。稀土的掺入使得晶相所对应的衍射峰强度变弱且峰形宽化,这说明适量Nd的掺杂使涂层表面TiO2晶粒细化了。结果表明,掺杂Nd元素的电极,掺杂比（质量比）为Ti：Nd=100：1、热处理温度为540℃、热处理时间为60min时电极催化性能最好,此电极对目标有机物CODCr去除率达到81.6％,而不掺杂稀土元素的Ti／TiO2电极为阳极时COD-Cr去除率在同样时间内仅为67．7％,说明稀土的掺杂有利于电极催化性能的提高。     

Demonstration of selected ion flow tube MS detection in the parts per trillion range

The rate coefficients of the ion-molecule reactions between H3O+, NO+, O2+, and phosphine were determined using a selected ion flow tube. Using these data, the selected ion flow tube mass spectrometry (SIFT-MS) method was applied to the real-time measurement of phosphine in nitrogen without sample preparation down to concentrations in the mid parts per trillion range. This is the first reported measurement using SIFT-MS in the parts per trillion range. Linear dependencies on concentration were found from 190 ppt to the ppm range, and the limit of detection for a 10-s scan was 190 ppt (0.27 pg/mL).     

Laser-induced breakdown spectroscopy of gas mixtures of air, CO2, N2, and C3H8 for simultaneous C, H, O, and N measurement

Laser-induced breakdown spectroscopy (LIBS) was applied for simultaneous measurement of the elements C, H, N, and O in CO2-air, C3H8-CO2, and C3H8-N2 gas mixtures at atmospheric pressure. A single 7-mm-diameter aperture at the sample chamber was used for 1064-nm Nd:YAG laser irradiation and plasma signal output to an echelle spectrometer. Double-pulse laser bursts of approximately 8-ns pulse width (FWHM) and 250-ns interpulse separation were applied to increase the plasma signal. Calibration curves of the LIBS signal versus the partial pressure or the atomic abundance ratios were taken by dilution series in intervals that are relevant in the combustion of heptane (C7H16) near an equivalence ratio of 1.     

Synthesis, characterization and thermolysis of 1,1-diamino-2,2-dinitroethylene (FOX-7) and its salts

The present paper discusses the efforts made in HEMRL to establish the synthesis of FOX-7 at 100 g/batch level. In the present study, 1,1-diamino-2,2-dinitroethylene has been synthesised by treatment of acetamidinium chloride with diethylmalonate to obtain 2-methyl-pyrimidine-4,6-dione which on nitration followed by hydrolysis gave FOX-7. The synthesised FOX-7 has been characterized by spectroscopic and thermal techniques. The data obtained confirms the structure of FOX-7. The sensitivity of FOX-7 towards mechanical stimuli indicated its insensitive nature. The theoretically computed explosive and ballistic parameters are close to that of RDX. The synthesised FOX-7 has been used as a precursor for the synthesis of potassium and guanidinium salts and the thermal analysis of these salts indicate their exothermic nature.     

二氧化氮差分吸收激光雷达拉曼激光源的优化研究

Nd:YAG三倍频激光(355nm)抽运高压CH4,获得其第一级斯托克斯光S1(395.60nm),作为NO2差分吸收激光雷达(NO2-DIAL)的激光源λon.通过增大激光脉冲宽度、改变拉曼池耦合透镜的焦距和气体压强等条件,获得了满足实际使用要求的转化效率高、稳定性好的395.60nm波长拉曼激光输出.该实验结果已应用于差分吸收激光雷达的NO2探测.     

Disturbance of laser-induced-fluorescence measurements of NO in methane-air flames containing chlorinated species by photochemical effects induced by 225-nm-laser excitation

Laser-induced fluorescence measurements of NO in CH(4)-air flames seeded with CH(3)Cl and CH(2)Cl(2) are described. The measurements are perturbed by strong photochemical effects characterized by UV emissions. The contribution of these background emissions is taken into account on the basis of an on-line-off-line resonance procedure. First results indicate an important increase of NO in the presence of chlorinated species. Background emissions observed in the range 220-260 nm and at 278 nm are ascribed, respectively, to electronically excited HCl and CCl photofragments. It is shown that C(2)H(3)Cl and CHCl(2) species are responsible for the formation of HCl and CCl, respectively, and a photolytic mechanism for formation of the photofragments is proposed.     

Detection of chromium in wastewater from refuse incineration power plant near Poyang Lake by laser induced breakdown spectroscopy

A laser induced breakdown spectroscopy (LIBS) system was developed for determination of toxic metals Cr in wastewater collected from a refuse incineration power plant near Poyang Lake. The plasma was generated by focusing a pulsed Nd:YAG laser at 1064 nm on the surface of liquid. Experimental conditions were optimized for improving the sensitivity and repeatability of the LIBS system through a parametric dependence study in potassium bichromate (K(2)Cr(2)O(7)) aqueous solutions. Calibration curves for Cr I 425.43 and 357.87 nm lines are compared and the limit of detection is found to be 39 and 86 ppm, respectively. This calibration curve of Cr I 425.43 nm has been used for quantification of Cr in wastewater collected from a refuse incineration power plant near Poyang Lake where the concentration of Cr is found to be 97 ppm. The results between LIBS and standard analytical technique such as atomic absorption spectroscopy were compared, and the relative standard deviation was 8.5%.     

Radiation-induced reduction of diuron by gamma-ray irradiation

Diuron degradation efficiencies and the proposed mechanism by gamma-ray irradiation were investigated. Several factors that might affect the degradation values were further examined. The UV absorbances at 200-400 nm and diuron concentration decreased with the increase of radiation dose. When diuron initial concentration was 18.5 mg L(-1) and 1.0 kGy was selected as the radiation dose, diuron removal value and loss of total organic carbon were 100 and 34.1%, respectively. However, the concentration of Cl- ion increased with the increase of radiation dose. The process could be depicted by first order reaction kinetics and the reaction was mainly caused by the reaction of diuron with .OH and eaq-. The degradation efficiency decreased with the increase of initial concentration at the same radiation dose. H2O2, HCO3-, NO3-, NO2-, CH3OH and humic acid as additives reduced the degradation efficiency. Furthermore, the increase of NO3-, NO2-, CH3OH and humic acid would result in the decrease of the degradation values. The pH value could affect the removal efficiency and the degradation process was enhanced in acid condition. The pH value became lower with increasing radiation dose after gamma-ray irradiation.     

Comparison of nanosecond and picosecond excitation for interference-free two-photon laser-induced fluorescence detection of atomic hydrogen in flames

Two-photon laser-induced fluorescence (TP-LIF) line imaging of atomic hydrogen was investigated in a series of premixed CH4/O2/N2, H2/O2, and H2/O2/N2 flames using excitation with either picosecond or nanosecond pulsed lasers operating at 205 nm. Radial TP-LIF profiles were measured for a range of pulse fluences to determine the maximum interference-free signal levels and the corresponding picosecond and nanosecond laser fluences in each of 12 flames. For an interference-free measurement, the shape of the TP-LIF profile is independent of laser fluence. For larger fluences, distortions in the profile are attributed to photodissociation of H2O, CH3, and/or other combustion intermediates, and stimulated emission. In comparison with the nanosecond laser, excitation with the picosecond laser can effectively reduce the photolytic interference and produces approximately an order of magnitude larger interference-free signal in CH4/O2/N2 flames with equivalence ratios in the range of 0.5< or =Phi< or =1.4, and in H2/O2 flames with 0.3< or =Phi< or =1.2. Although photolytic interference limits the nanosecond laser fluence in all flames, stimulated emission, occurring between the laser-excited level, H(n=3), and H(n=2), is the limiting factor for picosecond excitation in the flames with the highest H atom concentration. Nanosecond excitation is advantageous in the richest (Phi=1.64) CH4/O2/N2 flame and in H2/O2/N2 flames. The optimal excitation pulse width for interference-free H atom detection depends on the relative concentrations of hydrogen atoms and photolytic precursors, the flame temperature, and the laser path length within the flame.     

Synthesis of alkyl sulfonated fullerenes without catalyst: improved water solubility by the sulfonate groups

Two new alkyl sulfonated fullerene (C60) derivatives C60(O)14(OH)4(OCH2CH2CH2SO3Na)5 (2), C60(O)15(OSO3Na)5(OCH2CH2CH2SO3Na)6 (4) with high water-solubility were synthesized by different routes. One derivative (4) was facilely synthesized from a sulfonated C60 derivative C60(O)11(OH)4(OSO3Na)8 (3) in aqueous phase without the addition of any catalyst and has the highest water solubility (118 mg/mL) and smallest aggregation size (49.2 nm) in neutral aqueous solution (0.1 wt%). Derivative 2 was synthesized from fullerenol C60(O)8(OH)13 (1) directly in DMF affording enhanced water solubility compared to 1. The estimated average molecular formulae of these new alkyl sulfonated C60 derivatives were determined by XPS spectroscopy and confirmed by FTIR and 1H NMR spectroscopies. The measured water solubility of the sulfonated C60 derivatives follows the order of 3 < 2 < 4, suggesting that the larger number of functional groups is directly correlated to the higher water solubility, and the sulfonate groups can improve the water solubility greatly. The aggregation size of 2-4 measured by dynamic light scattering (DLS) is all smaller than that of fullerenol 1, indicating that more functional groups result in the improvement of the dispersion of fullerenol in water. ESR study indicates that 2-4 have the ability to produce stable radicals, and the intensity of the ESR signal decreases evidently with the increase of the number of functional groups from 3 to 2 to 4.