2000 Vol. 13, No. 2

Article
The phenomenon of false lines due to folding in Fourier Transform Spectroscopy is explained using by Nyquist sampling theorem The characters of false lines are discussed. The key to avoid false lines is to use suitable filters to remove the signal outside the wanted spectral region. Two kinds of filters, optical and electrpnic filters namely, are compared to serve this purpose. It is found out that both kind of filters should be combined in order to prevent folding as well as secure a good signal to noise ratio. Some experimental parameters setting rules are advanced. The method proved to be successful in our experiments of recording the v= 3 and v=4 highly vibrational spectra of arsine.
H/D exchange reaction properties of four cyclopropane derivatives were examined using D2O as reaction reagent under chemical ionization condition. The fragmentation properties of the product ions [M+1]+, [M+2]+ and [M+3]+ formed by ion-molecule reaction of four cyclopropane derivatives with the ion system of CD3OD were investigated by using collision-induced dissociation technique. The experimeat results indicate that the product ions are produced via the H/D exchange reaction between reactants and reactive reagent ions of CD3OD. The exchangeable hydrogen on the ring carbon bearing the isobutenyl (or dichloroethylene) groups is more active than that on the ring carbon bearing carbonyl group.
The characterization of photochemistry of 1, 2- and 1, 4-NQ in neutral aqueous solution was investigated by using 248 nm laser photolysis kinetic absorption spectra equipment.It was found that the maximum absorption peak of 1, 2-NQ and 1,4-NQ cation radical all were around 380nm, but two new species were formed with the decay of 1,4-NQ cation radical with the maximum absorption at 410 and 580nm respectively, data analysis demonstrated that the species with absorption at 410nn was assigned to the dehydrogenated radical, and the absorption at 580 nm could be attributed to the transient product of electron transfer process.Whereas 1,2-NQ in neutral aqueous solution can be monophotonic ionized by 248 nm laser.
The O-H stretching v =4, 5 vibrational overtone spectra of iso-propanol are measured by using highly sensitive cavity ring down spectroscopy (CRDS), where three peaks are observed for each vibrational level. They are assigned to the absorption of the O-H stretching vibrations of molecular conformations. Band intensity formula of overtone for CRDS is given,and band intensities of each band for different levels are obtained. Meanwhile, the mechanical frequencies X1, anharmonicities X2, and dissociation energies D are evaluated by the local mode theory. The different possible conformations of the molecule are optimized by density function theory (DFT) B3LYP/6-31+G* theory methods, where it is confirmed that only the two conformations of trans and gauche forms are stable in this molecule. The calculated O-H stretching frequencies and stability of the molecule are in good agreement with the experimental results.
The present work has derived the potential energy function for the ground state X1∑+of LaH in Murrell-Sorbie function form. In the first place, the electronic state and it′ s rea sonable dissodation limits are correctly determined based on Atomic and Molecular Reaction Statics (AMRS), and then, using the relativistic compact effective potential (RCEP) for La, the equilibrium geometry and dissociation energy for LaH have been calculated by the QCISD method. The calculated results for Re'De' Be' αe' ωe and ωexe are 2.125A, 2.623eV,3.7333cm-1, 0.0723 cm-1, 1461.73cm-1 and 21.383cm-1 respectively, which are in good agreement with experimental or calculated values in references.
We demonstrate the phenomenon of stochastic resonance in the bistable IodateArsenic (Ⅲ) reaction with a sinusoidal signal and a gauss white noise imposed on the flow rate by computer simulation. With the help of the signal and noise, the system hops between the two steady state. From the analysis of the time series output, the signal is amplified by noise.When stochastic resonance is achieved, the signal-to-noise ratio pass through a maximum at an optimal noise level.
Geometry and electronic structure of uranyl cations have been calculated with harmonicvibration analysis, using relativistic effective core pseudopotential (RECP) method. The calculated bond lengthes and vibrational frequencies have compared favorably with experimental value.U5f-O2p bond dominates in the U-O bonding, while there are strong bonds between U6p,U6d, U7s and d-s hybridizing orbitals with O2s atomic orbital. The calculated results with different spin multiplicity show that the ground state of UO22+ prefer 1∑g+.
The potential energy surface of the reaction of O atom with HOBr is studied by Density Functional Theory (DFT). Structure parameters, vibration frequencies and energy of each stationary point on its potential energy surface are given. B3LYP method is applied in the calculations. Results illustrate that on the potential of the reaction there are two channels, which are simply marked by abstracting O and abstracting Br, respectively. Evidently, the two channels have the same products. The exothermic energy (42.26kJ/mol) of the reaction is given and the calculated heat of formation of HOBr agrees well with the experiment result through taking advantage of the character of isodesmic reaction.
The highly excited vibrational spectrum of OH bond in H2O molecule is calculated in a U(2) algebraic model, and the calculation is compared with those by other new models. The result shows that the algebraic model is useful to describe vibrational spectrum of OH bond in this molecule with a smaller standard deviation.
The degeneracy appears generally in the energy level spectra. It is related closely to the symmetrical character of the corresponding Hamiltonian random matrix. According to the fact that the state space of Hamiltonian matrix for degenerated spectra can be expanded into a series of sub-space corresponding to different eigenvalues, the degenerated spectra is dealed with by a special way. By introducing weights of the levels, the accumulative function curve of the degenerated spectra is smoothed. Therefore the fluctuation spectra can be unfolded by means of polynomial expansion fitting with weights. Then a set of methods that are used to analyses statistical character of fluctuation such as the NNS distribution, the spectra rigidity and the fractal dimension function for energy levels are suggested. Further more, the degenerated spectra such as the vibrational energy spectra of the molecules of H2O、 NH3、 CH4 are analyzed with this method. It's tums out that both their regular spectra and reduced non-degenerated spectra are nonpoissonized, further more, the former is obviously further nonpoissonized compared with the latter,i.e.,the level repulsion of the reduced non-degenerated spectra is greater than the corresponding regular one. However, the statistic character of fluctuations in energy spectra of the H2O, NH3, CH4 are different because of their degeneracies: they transform from the obviously nonpoissonized type to the closely poisson type.
The EPR theory of the full configuration has been established for a 4A2(3d3) state ion in the intermediate crystal field scheme. The EPR parameters are investigated in detail as functions of the cubic Dq and the trigonal crystal parameters V and V', the analytical perturbation expressions for the ZFS parameters D and Zeeman g factor are examined based on simultaneous diagonalization and find that Macfarlane's expressions work well indeed. The microcosmic origin of the EPR parameters have been studied, and indicates that the contribution of the spin doublets for the ZFS parameter D is very important, and for the ground state g factor it can be omitted.
The theoretical study on a series of complexes between nitrogenous aromatic compounds (C4H5N, C6H5NH2, C5H4NC1, C5H5N and C4H4N-) and CHC13 via weak chemical interaction was carried out. The complexes were considered as super molecules and calculated with DFT method at B3LYP/6-311G(d,p) level. The regularities of the stability, the charge transfer between the doner and accepter and the change of geometric parameters of the complexes were investigated. The results show that a series complexes can be formed from nitrogenous aromatic compounds (C4H5N, C6H5NH2, C5H4NC1, C5H5N and C4H4N) and CHC13via a weak chemical interaction. Especially, the one with negative charge (C4H4N-) can form a more stable complex with CHCl3. The calculation results also show that there is an obvious charge transfer in the complex-forming process. In addition, the regularity of stabilities of the complexes is well consistent with that of the developed hydrogen-bonding lengths, and basically consistent with that of amount of the charge transfer too.
Porous-type anodization is carried out on thin aluminum film deposited on silicon substrate by electron beam evaporation technique. TEM examination of the obtained alumina film shows a much more less ordered pore arrangement compared with those produced from bulk aluminum under long anodization period condition. This discrepancy in pore ordering degree can be caused by many factors such as anodization period, applied electrolyte and voltage.Furthermore, a newly introduced crystallinity should also be carefully taken into account. Due to the polycrystalline structure of the thin A1 film rather different from that nearly single crystalline of bulk Al, the inteffacial region of its Al grains, which induces some extent of fluctuation in atomic density and relative anodizing rate along the direction of the pore development in comparison with groins themselves, will give an effect to the self-organized process during anodization by disturbing the electric field distribution at the pore bottom.
The structure and discharge/charge characteristics of ZnO elctrode and Zinc-based composite oxide films prepared by pulsed laser deposition (PLD) are investigated by XRD and discharge/charge measurements.The results suggest that the insertion capability of ZnO electrodes increases with the annealing temperature, and might be related to the presence of oxygen deficient and the formation of Zn1+δO. The addition of other oxides such as B2O3, NH4H2PO4 and Al2O3 into ZnO are found to improve significantly the electrochemical properties of film electrodes, and the insertion capability of the zinc-based composite oxide film electrode depends strongly on the deposition condition. For a typical deposition condition with ambient argon of 25Pa and the substrate temperature of 400℃,and a target with a nominal composition of Zn:B:P:A1=1:1:0.5:0.5,the deposited zinc-based composite oxide film exhibits superior capability and well cyclibility.
By using n-butylamine and Rhodamine (R6G)/Polyglycol as the carbon resource and the vapour resource, carbon-films and mixed-films were prepared respectively by means of radio frequency light discharge and conventional vacuum vapour deposition. Raman spectra and IR spectra of the carbon-films indicate that therer are amino groups and hydrogen in the carbon-films, which is, probably, the cause of the blue-shifting broadening and higher emission intensity of the peak in their fluorescence spectra.
Monodispersed polymer modified metal iron particles have been synthesized by y-ray radiation. Selecting cetyltrimethyl ammonium bromide (CTAB), sodium dodecyl sulfonate (SDS),Tween-80, TritonX-200 and OP-10 as emulsifiers respectively. Several emulsions containing organic monomers and iron particles were obtained. By comparing stability of these emulsions,we selected a more suitable emulsifier, TritonX-200. Polymer modified iron particles were characterized by XRD, TEM and IR. In addition, pure iron particles and polymer modified iron particles were dispersed into mineral oil respectively to form magnetorheological fluids and their differences in suspension properties have also been investigated. The differences in magnetorheological measurement between suspension of Fe-copolymer particles and Fe3O4-PMMA composite particles have been studied. Experimental results showed that this kind of suspension with Fe-copolymer particles dispersed will become a new type of magnetorheological materials.
Mg(A1)O composite oxides obtained from hydrotalcite compounds upon calcination at 673、 873 and 1073K, respectively, show the pattems of MgO by X-ray difffraction measurements. The samples calcined over 873K also show the patterns of MgA12O4 spinel.Microcalorimetric measurements of NH3 and CO2 adsorptions were used to determine the strength and density of these sites. It is discovered that the basicity sequence is MAO-2>MAO-3≈MAO-1, while acidity order is MAO-1>MAO-3≈MAO-2. NH3 and CO2 molecules were used as the probing molecutles to investigate the nature of acid and base sites on Magnesium-Aluminium composite oxides. Infrared spectroscopic studies of these adsorped molecules indicated that the acid sites were mainly Lewis acid sites, whereas the base sites were surface oxygen anions. The results showed that the calcination temperature has little influence on the nature of surface base sites. Results of solid-state magic-angel-spinning 27Al NMR revealed that significant transitions of coordinate state for Al3+occur in the samples upon calcination at 673、873 and 1073K, respectively.
Using crude materials of industrial product TiCl4, ordinary reagent Sr(NO3)2 and KOH, by adding surface active agent dodecylbenzenesulphonic acid (DBS), the nanosized SrTiO3 partide modified with a layer of DBS were successfuly prepared through the hydrothermal method and their microstructure were characteried. FTIR, DAT and TG were used for the determination of the components. It can be proved that the nanosized SrTiO3 were capped by a layer of DBS. The sizes, shapes and crystal phase were determined by TEM and XRD. The results indicate that the product are cabic phase, small crystal (size distribution and Little agglomeration. The average size of the powders is about 120nm. The average size of layer of DBS is about 6 nm. In contrast with the bulk SrTiO3 The polarity of nanometer SrTiO3 powder wass changed by coating with a layer of DBS.
The activities of activated carbon fibers(ACFs) from ethylene tar pitch (ETP) and cellulose were examined for the oxidative conversion of SO2 into aq. H2SO4 in the presence of O2 and H2O. The results indicated that Cellulose ACF showed much higher activity than ETP ACF, owning to higher ability of SO2 adsorption, higher catalytic activity for the oxidation of SO2 to SO3 and larger amount of H2O adsorption, enhanced catalytic activity for the oxidation of SO2 to SO3 showed highest among these abilities. These in turn depend on nitrogencontaining group and some oxygen-containing group in the surface of cellulose ACF, so the SO2 removal activity of ACFs is affected by functional groups.
The effect of CrOx on resisting nodulizing of ZrO2 and the dispersion state of CrOx have been studied using XRD and BET techniques. The results indicate that CrOx is an effctive antisintering agent for ZrO2, and it also opposes the tetragonal → monoclinic transition. The strong interaction between CrOx and ZrO2 is beneficial to the dispersion of CrOx on ZrO2 surface. The TPD-MS experiments of NO show that there are two types of adsorbed NO species which interact with CrOx/ZrO2 catalyst in differrent strength. Dissociation of NO occurs in the process of temperature programmed desorption. The experiment indicates that N2O is an intermediate of NO-CO reaction. At lower temperature large amount of N2O will be produced while amount of N2 will be larger at higher temperature.
The molecular orbits of CO are rearranged under the strong influence of coadsorbed Cs atoms. HREELS study shown that there are two molecular adsorption states of CO on a Cs pre-covered Ru(1010) surface. One with high C-O stretch frequency similar to that on clean Ru(1010) surface, the other with low C-O stretch frequency due to the strong short-range interaction between the CO molecule and the Cs atom. ARUPS experiment results shown the peak for CO on dean Ru(1010) surface, at 7.5eV BE attributed to the 5σ and 1πorbits, is split into two peaks with one at 6.3 eV BE and the other at 7.8 eV BE. Two concrete models has been proposed to describe the short-range alkali metal-CO interaction, the sp2 rehybridization model and the direct interaction model. The experiment results confirm that the sp2 rehybridization model must be reasonable. According this model, the Me-CO bond rehybridizes to sp2 forming new a and πt bonds (a1' b1' b2 orbits in the C2v point group) According The p-polarized ARUPS results, the peak at 6.3eV BE, comes from one of a π type lb2 orbits, shows an anti-symmetry character about the plane parallel to the <0001>crystallographic direction in the surface. Another π type orbit 1b1 is still at 7.8eV BE overlapping with 5a1 orbit.
A system for measuring nonlinear dielectric permittivity has been set up. The third order nonlinear dielectric permittivities of ferroelectric ceramic (PT, BT, PZT)/VDF-TrFE 0-3 composite thick films have been measured at the electric field ranging from 1 to 10 MV/m (f0= 1kHz) and at the temperature ranging from ambient temperature to 140℃ . It is found that the third order dielectric permittivity ε3 of three kinds of composite increases with the increase of ceramic volume fraction φ ε3 of the composite also shows a dependence on electric field. A higher electric field produces a lower ε3, but BT/P[VDF(70)-TrFE(30)] and PZT/P[VDF(77)-TrFE(23)] whose φ is higher than 0.4 show a minimum at 6MV/m of electric field.ε3 of the composite which two phases being poled is less than that of the composite which only the ceramic phase being poled. The temperature spectra of ε3 for PZT/P[VDF(77)-TrFE(23)] also produces an apparent thermal hysteresis phenomenon similar to that of ε1.