Kinetic studies of antimony and selenium atomization processes including a chemical modifier during their determination by electrothermal atomic absorption spectrometry

We have studied antimony and selenium atomization processes including a chemical matrix modifier (palladium-containing activated carbon) during their determination by electrothermal atomic absorption spectrometry. We have developed and fine-tuned an experimental setup for determining the kinetic characteristics (activation energy and frequency factor) for element atomization processes from measurements in the initial section of the analytical signal. We provide a rationale for the most likely mechanism for the interactions that occur. The results of the kinetic studies of the atomization processes showed that the modifier we developed was highly effective, as a result of formation of a thermally stable condensed system C-Pd-A (where A is the analyte). __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 530–534, July–August, 2006.     

Chaotic oscillations and noise transformations in a simple dissipative system with delayed feedback

We analyze the statistical behavior of signals in nonlinear circuits with delayed feedback in the presence of external Markovian noise. For the special class of circuits with intense phase mixing we develop an approach for the computation of the probability distributions and multitime correlation functions based on the random phase approximation. Both Gaussian and Kubo-Andersen models of external noise statistics are analyzed and the existence of the stationary (asymptotic) random process in the long-time limit is shown. We demonstrate that a nonlinear system with chaotic behavior becomes a noise amplifier with specific statistical transformation properties.     

Electronic spectra of cationic forms of meso-tetrapropylporphin in a nanoporous silicate gel matrix

We have studied the fluorescence and fluorescence excitation spectra at 300 K, 77 K, and 4.2 K for silicate gel matrices colored with meso-tetrapropylporphin by impregnation of the matrix with a solution of the pigment. Comparison of the data obtained with the absorption spectra in acidified solutions and analysis of the low-temperature fine-structure vibronic spectra, and also taking into account data obtained earlier for octaethylporphin in a xerogel showed formation of two cationic forms of meso-tetrapropylporphin in the gel matrix: the short-wavelength form has a dicationic structure, while the long-wavelength form has a monocationic structure. We have traced out the correlations of the vibrational structure in the spectra of the dicationic form with data for the porphin dication, and we have drawn a number of conclusions concerning the normal vibrational modes that are active in the vibronic fluorescence and absorption spectra of the studied cationic forms. Using the AM1 semiempirical quantum chemical method, we optimized the geometry of the mesotetrapropylporphin dication: the most stable of the possible conformers is the dication structure with saddleshaped macrocycle nonplanarity. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 453–461, July–August, 2006.     

Time-resolved fluorescence spectra of a bichromophoric molecule, 2-methyl-1,2,3,4-tetrahydroisoquinoline in various media

Time-resolved fluorescence spectra of a title molecule (with benzene and aliphatic amine parts) in various media, after excitation by several lasers were observed to complement the previous work by conventional spectroscopy [N. Kanamaru, J. Tanaka, J. Phys. Chem. 95 (1991) 6441]. Though complex with many new features, the results were roughly consistent with the previous ones. The significant conclusions are as follows: (1) The emission to be ascribed to the amine (N) part, with more than one component (of nN and aN types) is observed not only for the acetonitrile solution (as previously reported) but also for all the other media. (2) Contrary to the case of a nonpolar hexane solution, both of N fluorescences in the other media reveal unusually long-lived decay components. This can be interpreted by assuming the so-called charge-transfer-to-solvent (CTTS) state that is nonfluorescent and lies just below the fluorescent state. (3) This observation in the protic media can also be taken as another evidence of the peculiar hydrogen bonding between this amine and the protic solvent molecules [N. Kanamaru, J. Tanaka, J. Phys. Chem. 95 (1991) 6441]. (4) Thus, the unexpectedly large quantum yields of N fluorescences in the polar media are now interpreted as arising due to the slow S₁^N→(CTTS)→S₀ internal conversions.     

Monitoring the Aggregation of Dansyl Chloride in Acetone through Fluorescence Measurements

The aggregation of dansyl chloride (DNS-Cl) in acetone has been studied in detail by steady-state fluorescence techniques.It has been demonstrated that DNS-Cl is stable in acetone during purification and aggregation study processes.The aggregates are not solvolyzed in acetone,and do not take part n any chemical reactions either.It has been found that DNS-Cl tends to aggregate even when its concentration is much lower than its solubility in acetone.The aggregation is reversible,and both the aggregation and the deaggregation are very slow processes.Introduction of SDS has a positive effect upon the formation and stabilization of the aggregates.     

一类新的表面活性剂——长链烷基三苯基鏻——Ⅵ.稳态荧光猝灭法测定十二烷基三苯基溴化鏻胶束的平均簇集数

研究了十二烷基三苯基溴化鏻(C_(12)PBr)胶束中N,N-二甲基苯胺(DMA)和二苯甲酮(DPK)对芘的荧光猝灭,发现DMA的猝灭行为不符合Stern-Volmer动态猝灭和Turro静态猝灭模型;DPK的猝灭行为不符合Stern-Volmer猝灭模型,但遵从Turro静态猝灭模型。根据DPK的静态猝灭性质测得C_(12)PBr胶束的平均簇集数为15士2,并相应地得到C_(12)PBr的临界胶束浓度为(1.77±0.09)×10~(-3)mol/L,后者与文献值一致。     

Laser vaporization: A versatile method for studying metal clusters

Vaporizing solid samples of metals and semiconductors with a YAG Laser is a method well suited for producing molecules and clusters of those materials. The clusters are examined by either laser-induced fluorescence (LIF) or mass spectroscopic methods. The technique is valuable for both gas phase and matrix studies. The method is described and some applications, studying either the structure of small metal molecules or their reactions, are reviewed, with emphasis on our recent results from the LIF studies of LiBe, Al₂ and the reaction of Al with oxygen, yielding A1₂O. For larger clusters, Ion Cyclotron Resonance is an extremely valuable method, as we demonstrate by its application to the reactions of small charged silicon clusters with strong oxidising agents.     

应用LiNbO_3声表面波驱动的全光纤声光频移器

介绍一种工作在10.7MHz的全光纤声光频移器.它由在LiNbO_3基片上制作的叉指电极换能器产生的声表面波驱动.当驱动电功率1.5W时,频移光转换效率达35％.     

Study of photon-induced L3 vacancy alignment for elements La to U

Alignment of photon-induced L₃ vacancies is studied in rare earth and highZ elements at energies of experimental interest, near thresholds to 60 keV, under nonrelativistic dipole approximation. Numerical calculations of the matrix element are undertaken to produce theoretical data for comparison with the experimental findings. The A₂ values being s>0.1 at photoelectron energies <20 keV are certainly higher than 5–8% uncertainties quoted in experimental results. Present findings are from a very basic model, hydrogen-like and can further be treated as reference to observe the impact of screening, relativistic, multipole and retardation corrections to the model     

(NH4)2MoS4在活性炭上浸渍过程的研究:Ⅱ.干燥机理及模型

（ＮＨ＿４）＿２ＭｏＳ＿４在活性炭上浸渍过程的研究Ⅱ．干燥机理及模型秦慧芳，张成芳，陆岗，俞丰，朱子彬（华东理工大学无机化工研究所，上海２００２３７）２３７）关键词硫代钼酸铵，活性炭，干燥，钼分布，干燥模型负载型催化剂的活性组分在载体上的分布，受浸渍...