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101.
研究了4-位苯基取代基旋转受阻和旋转自由的2,4,6-三苯基氧盐的光物理性质。实验结果表明,当4-位苯基取代基旋转受阻时,氧盐化合物在激发态时引起的分子内极化程度比4-位取代基旋转自由的氧盐化合物大,即在激发态时旋转受阻氧盐化合物发生的分子内电荷转移能力较强;4-位取代基旋转自由的化合物的荧光量子产率随溶剂粘度的增大而有所增大,但旋转受阻化合物在相同的条件下则出现相反的结果。实验结果还表明,4-位取代苯基旋转受阻对化合物的荧光发射不利。 相似文献
102.
通过流动相中电解质浓度对毛细管电色谱柱效能的流动相平均线速度的影响,研究了CEC中双电层叠加现象。提出选择合适电解质组成的浓度及在制备色谱柱过程中避免细小和破碎的固定相颗粒进入柱中,以有效地减小双电层叠加作用。 相似文献
103.
La2O3,Y2O3-Mo次级发射材料研究 总被引:2,自引:1,他引:2
采用粉末冶金方法制备了La2O3,Y2O3-Mo次级发射材料,测试了各种材料的次级发射系数。结果表明在钼中加入稀土氧化物可以具有很好的次级发射性能。经过激活处理后,材料的最大次级发射系数均高于2.0,达到了材料使用要求的发射水平。应用扫描电镜(SEM)和光电能谱仪(XPS)研究了稀土元素在烧结体断口和发射前后在试样表面的分布情况。分析结果表明稀土元素易于在晶界处偏聚,且发射后试样表面稀土元素的相对浓度明显高于发射前的浓度。 相似文献
104.
A systematic extension of Ruedenberg's expansion formula is applied to evaluate two-electron integrals occurring in calculations on molecular structure. Minimum STO basis sets are used for all SCF-calculations within the framework of the MEDO-method (Multipole Expansion of Diatomic Overlap). The errors due to this approximation scheme are almost negligible compared to those introduced by the truncated basis set: LiH, Li2 and N2 are chosen as examples. 相似文献
105.
We present a systematic procedure for the optimization of the expansion basis for the limited expansion of diatomic overlap density functional theory (LEDO-DFT) and report on optimized auxiliary orbitals for the Ahlrichs split valence plus polarization basis set (SVP) for the elements H, Li--F, and Na--Cl. A new method to deal with near-linear dependences in the LEDO expansion basis is introduced, which greatly reduces the computational effort of LEDO-DFT calculations. Numerical results for a test set of small molecules demonstrate the accuracy of electronic energies, structural parameters, dipole moments, and harmonic frequencies. For larger molecular systems the numerical errors introduced by the LEDO approximation can lead to an uncontrollable behavior of the self-consistent field (SCF) process. A projection technique suggested by L?wdin is presented in the framework of LEDO-DFT, which guarantees for SCF convergence. Numerical results on some critical test molecules suggest the general applicability of the auxiliary orbitals presented in combination with this projection technique. Timing results indicate that LEDO-DFT is competitive with conventional density fitting methods. 相似文献
106.
辉光放电原子发射光谱法快速分析生铸铁 总被引:3,自引:0,他引:3
通过对辉光光源参数-放电电流、放电电压、预溅射时间和分析时间对生铸铁标样放电强度和稳定性影响的研究,优化光源参数,建立了辉光放电原子发射光谱法同时测定生铸铁中碳、硅、锰、磷、硫等12个元素的快速分析方法。分析生铸铁试样时发现了不同灰口铸铁在碳分析结果方面存在偏差,对碳的偏差进行了讨论并通过制样条件和光源参数的调整可以有效地减小偏差。通过对不同生铸铁样品进行准确度和精密度试验,结果表明:分析结果与标准值或化学法结果一致。分析一件试样的时间仅需2~5 min。 相似文献
107.
Mohamed Boumerzoug Marcel Boudreau Peter Mascher 《Plasma Chemistry and Plasma Processing》1997,17(2):181-192
Real-time optical emission spectroscopy (OES) was used to monitor the deposition of TiN both from mixtures of tetrakis(dimethylamino)titanium
(TDMATi)-N2 and TiCl4-H2-N2 in an electron cyclotron resonance chemical vapor deposition system. The accurate control of the ratio of the emission intensities
of ionized nitrogen at 391.4 nm and molecular nitrogen at 357.7 nm (N
2
+
/N2) led to low temperature deposition of stoichiometric TiN (Ti/N ≈ 1) and very low resistivity in both cases. It was found
that high ion density plasmas are crucial for a considerable reduction of the deposition temperature while maintaining good
film quality. OES shows that the abundance of certain excited plasma species is not only dependent on the gas mixture and
the deposition parameters, such as total pressure and microwave power, but also is strongly affected by the magnetic field
configuration. The deposition rate and the film resistivity can be related to the emission intensity ratio, I(N
2
+
)/I(N2). Finally, the two processes are compared in terms of the quality of as-deposited and heat-treated films. The comparison
shows that the films obtained with TDMATi exhibit lower resistivity and are thermally more stable than with TiCl4. 相似文献
108.
Davis JM 《Journal of separation science》2005,28(4):347-359
The low prediction by statistical-overlap theory of the numbers of singlets and peaks in two-dimensional separations containing zones represented by either circles of small number or eccentric ellipses of any number is shown to result from use of probability expressions for unbound spaces of infinite extent. An exact theory is derived for the probability of singlet formation in a reduced two-dimensional space of unit length, width, and area. The probability is a weighted sum of the probabilities of singlet formation in the interior, edge, and corner regions of the space, which depend only on saturation. The weighting factors are the fractions of area associated with each region and depend on the number of zones, the aspect ratio, the saturation, and the ellipse's spatial orientation. The average numbers of doublets, triplets, and peaks in the space are approximated by combining these results with Roach's equations describing the clustering of circles in an unbound two-dimensional space. Simulations show that theory predicts the number of singlets, doublets, triplets, and peaks, when the number of zones is 25 or more, the aspect ratio is 100 or less, and the saturation is 2 or less. The relationship is derived between the aspect ratios of ellipses in the reduced space and actual separation space. Calculations are presented for comprehensive two-dimensional gas chromatography. 相似文献
109.
This paper proposes a quick, novel method for tin determination in organotin chemicals by slurry nebulization inductively coupled plasma atomic emission (ICP-AES) spectrometry. The method was tested by the measurement of five organotin carboxylate complexes of known composition for obtaining simple stoichiometric data. The slurries were prepared by first dissolving the organotins in an adequate solvent (methanol, pyridine or acetone) well miscible with water and then adding this solution drop-by-drop to a 0.005% TX-100 tenzide solution while maintaining intensive mixing. Dynamic laser light scattering experiments showed that the average equivalent particle size in the resulting slurry was ≈0.3 μm for all samples and solvents. Under suitable ICP-AES measuring conditions, the signal recoveries were found to be between 101.8 and 106.6%, which allowed direct nebulization and calibration against aqueous solutions. Typically, 70 μg l−1 detection limit and 1–5% relative S.D. on five replicates can be achieved by the described method. 相似文献
110.
An inductively coupled plasma atomic emission spectrometry (ICP-AES) procedure has been developed and examined for the determination of boron content (0.01 up to about 2% B) in boron-alloyed steels such as POLDI ATA BOR (65% Fe, 19%Cr, 12% Ni, 1.5% Mn, 1% B), POLDI ATA BOR EXTRA (62% Fe, 18% Cr, 13% Ni, 2.5% Mo, 1.5% Mn, 1% B) and POLDI ATA BOR-R (75% Fe, 18% Cr, 3.5% Ti, 1.8% B). The steel sample is dissolved with a mixture of hydrochloric, nitric, sulfuric and phosphoric acids in a quartz vessel. Borides of alloyed metals, especially of iron and chromium, are quantitatively decomposed. The presence of phosphoric acid in a sample solution reduces the volatility of boric acid with water vapour.Presented in part at the 1989 European Winter Conference on Plasma Spectrochemistry, Reutte, Austria 相似文献