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191.
Hydrogen sulfide clusters generated by ultrasonic expansion of an H2S-Ar mixture into a vacuum were detected by electron impact mass spectrometry. The mass spectrum of the dimer, (H2S)2, was obtained under conditions of predominant dimerization. A mechanism of the formation of ions that involves intracluster reactions between the fragment ions of the monomer and the monomer molecule has been suggested.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 839–844, May, 1995.The work was carried out with the financial support of the Russian Foundation for Basic Research (Project No. 93-03-4933). The authors are also grateful to the European Environmental Research Organisation (EERO) for support. 相似文献
192.
Qiong Yu Lai Ji Zheng LuXiao Bo Su Xiao Yang Ji 《Journal of solid state chemistry》2002,165(2):312-316
Spinel compound LiNi1−xMnxVO4 (0≤x≤0.4) had been prepared by using the moist chemical method. X-ray diffraction spectra showed that the lattice constant increased with x in the LiNi1−xMnxVO4, XPS spectra indicating that Li1s had a chemical shift towards lesser binding energy, and manganese in LiNi1−xMnxVO4 existing as the mixed valence of Mn2+ and Mn3+. The electrochemical charge and discharge testing at a current density of 0.1 mA/cm2 between the potentials of 4.0 and 3.0 V vs Li/Li+ in 1 mol/dm3 LiPF6/EC+DEC (1:1 by volume) at 25°C showed that LiNi1−xMnxVO4 cell has a better rechargeability, but a lower cell voltage of 4.0 V vs Li/Li+ than that without the doping sample, and the capacity and the cycle efficiency of the Li/LiNi1−xMnxVO4 cells increased with x in the LiNi1−xMnxVO4. 相似文献
193.
In this paper, 2-(2′-hydroxy-phenyl)-4(3H)-quinazolinone (HPQ), a typical compound that exhibits excited state intramolecular proton transfer (ESIPT) reaction and possesses good photophysical properties, is synthesized and used as fluoroionophore for Fe3+ sensitive optochemical sensor. The decrease of fluorescence intensity of HPQ membrane upon the addition of Fe3+ was attributed to the blocking of ESIPT reactions of HPQ and quenching its fluorescence. The effect of the composition of the sensing membrane was studied, and experimental conditions were optimized. The sensor shows a linear response toward Fe3+ in the concentration range of 7.1 × 10−7 M to 1.4 × 10−4 M with a limit of detection of 8.0 × 10−8 M, and a working pH range from 2.5 to 4.5. It shows excellent selectivity for Fe3+ over a large number of cations such as alkali, alkaline earth and transitional metal ions. The proposed sensor is applied to the determination of the content of iron ions in pharmaceutical preparations samples with satisfactory results. 相似文献
194.
Massimo Ragazzi Paola Carbone Dino R. Ferro 《International journal of quantum chemistry》2002,88(5):663-669
Cycloolefin copolymers (COC) have recently raised much interest because of their excellent thermal and optical properties, largely determined by the chain composition and stereochemistry. Previous force‐field computations allowed us to define the main conformational characteristics of ethylene–norbornene (E–N) copolymers and to contribute to the elucidation of their microstructure on the basis of empirical relationships between conformation and 13C nuclear magnetic resonance (NMR) chemical shifts. A thorough test of ab initio 13C chemical shifts computations [gauge‐invariant atomic orbitals (GIAO)] on known cases shows that the agreement with experimental data is quite good, especially with the MPW1PW91 density functional theory (DFT), using the 6‐311+G(2d,p) basis set on properly energy‐minimized structures. We applied this method on proper model compounds to confirm the signal assignment of the spectra of E–N copolymers in the presence of norbornene microblocks, where strong effects arising from ring distortions are expected to occur. The results nicely confirm the latest assignment of norbornene signals belonging to ENNE sequences. This shows the great potentialities of GIAO/DFT computations with regard to complex spectra interpretation and polymer microstructural investigations. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002 相似文献
195.
Gerhard BringmannStefan Busemann 《Tetrahedron》2003,59(8):1245-1253
The first quantum chemical calculation of the circular dichroism (CD) spectra of michellamines has been achieved, based on a complete quantum chemical conformational analysis. Michellamines are dimeric naphthylisoquinoline alkaloids and thus naturally occurring quateraryls, with a large molecular size and flexibility and equipped with stereogenic centers and axes. 相似文献
196.
197.
M. Asmann A. Wank H. Kim J. Heberlein E. Pfender 《Plasma Chemistry and Plasma Processing》2001,21(1):37-63
Enthalpy probe measurements were taken of the converging plasma plume in a triple torch plasma reactor and related to substrate heat flux measurements. Results show excellent entrainment of process gases injected into the converging plasma plume by way of the central injection probe. At lower pressures (40 kPa), the plasma volume is equivalent to at least a 3 cm diameter, 4 cm long cylinder, with relatively uniform temperature, velocity, and substrate heat flux profiles when compared to a typical dc arc jet. Converging plasma plume size, substrate heat flux, and enthalpy profiles are also shown to be a strong function of applied system power. Substrate heat flux measurements show smaller radial gradients than enthalpy probe measurements, because of the high radial velocity component of gases above the substrate boundary layer. Enthalpy probe measurements were also conducted for diamond deposition conditions and approximate temperature and velocity profiles obtained. Problems with the uniform gas mixture assumption prohibited more accurate measurements. Reproducibility of enthalpy measurement results was shown with an average standard deviation of 11.8% for the velocity and 7.6% for the temperature measurements. 相似文献
198.
Ai Suzuki Parasuraman Selvam Tomonori Kusagaya Seiichi Takami Momoji Kubo Akira Imamura Akira Miyamoto 《International journal of quantum chemistry》2005,102(3):318-327
The decomposition reaction dynamics of 2,3,4,4′,5‐penta‐chlorinated biphenyl (2,3,4,4′,5‐PeCB), 3,3′,4,4′,5‐penta‐chlorinated biphenyl (3,3′,4,4′,5‐PeCB), and 2,3,7,8‐tetra‐chlorinated dibenzo‐p‐dioxin (2,3,7,8‐TCDD) was clarified for the first time at atomic and electronic levels, using our novel tight‐binding quantum chemical molecular dynamics method with first‐principles parameterization. The calculation speed of our new method is over 5000 times faster than that of the conventional first‐principles molecular dynamics method. We confirmed that the structure, energy, and electronic states of the above molecules calculated by our new method are quantitatively consistent with those by first‐principles calculations. After the confirmation of our methodology, we investigated the decomposition reaction dynamics of the above molecules and the calculated dynamic behaviors indicate that the oxidation of the 2,3,4,4′,5‐PeCB, 3,3′,4,4′,5‐PeCB, and 2,3,7,8‐TCDD proceeds through an epoxide intermediate, which is in good agreement with the previous experimental reports and consistent with our static density functional theory calculations. These results proved that our new tight‐binding quantum chemical molecular dynamics method with first‐principles parameterization is an effective tool to clarify the chemical reaction dynamics at reaction temperatures. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 相似文献
199.
Chemical sensors have been widely used for the analysis of volatile organic compounds. Employing chemical sensors in an array format with pattern recognition provides a higher degree of selectivity and reversibility leading to an extensive range of applications. When such systems are used for odour analysis they are termed electronic noses. Application of electronic noses ranges from the food industry, medical industry to environmental monitoring and process control. Many types of different gas sensors have been employed in the array. These include conducting polymers, metal oxide semiconductors, piezoelectric, optical fluorescence and amperometric gas sensors The transducer principle of these sensors is varied and is discussed in detail within this review. Examples of the current trends in sensor array technology as well as the applications to which the sensor-based noses have been applied are also discussed. 相似文献
200.
介绍废弃线路板中有回收价值元素和有害物质分析的采样、制样及检测技术。样品经过分类采样、剪切破碎和高温灰化制样,采用样品全分析或副批混合样分析。通过提高称样量、多次测定求平均值的办法,火试金富集-重量法测定贵金属金、银。湿法王水溶解样品,碘量法测定主体元素铜。电感耦合等离子体发射光谱(ICP-AES)法测定其它杂质元素,被测元素质量浓度在0~10μg/mL范围内与光谱强度呈良好线性关系,相关系数均大于0.9998。测定结果的相对标准偏差小于10%(n=5),加标回收率为97.0%~102.5%。该方法简单、快速,有效地解决了线路板样品不均匀而难采样,以及硬度、韧性强制样难,金属易包裹难分解的技术瓶颈,测定结果准确,具有代表性。该方法适用于废弃线路板化学成分分析,其它废弃电子产品检测可参考此方法。 相似文献