2000 Vol. 13, No. 3

Fe-Se binary cluster ions produced by direct laser ablation,were studied with a tandem time-of-flight masss pectrometer.It was found that FenSen+,FenSen-1+ in cluster cations,FenSen-FenSen+1-in cluster anions were main compositions of binary cluster ions.The photodissociation of cations FenSen+showed that FenSen+,FenSen-1+ were main photofragments,confirming their special stablity.The possible structures of Fe2Se2+ were calculated by Density Function Theory(B3LYP/LANL2DZ).
By using the new designed pulse photoemission gun,the energy distribution of photoemision electron beam,the relationship between the number of photoemission electrons and the intensity of laser and the duration of photoemission electrons in ionization region were studied.Most of electrons have the excess energy which laser induce photoemission electrons leave,but the energy distribution of electrons is widened by the space charge effect of electrons.For on pulse,photoemission electron density with about 109~1010/cm3 in the ionization region was found.
The correlation function-hyperspherical harmonic(CFHH)and generalized Laguerrefunction (GLF) method has been used to directly solve the equations of the n1,3P(n=1,2,3)low-lying excited states for the heliumlike systems.The eigenenergies of the helium atom are,-2.13317 Eh(13P),-2.12383 Eh(11P),-2.05810Eh(23P),-2.05516 Eh(21P),-2.03235 Eh(33P)and-2.03109Eh(31P),respectively,which agree well with the literature data at the sixth figure.The result shows that the CFHHGLF method is also well siuted for the 1,3P states of the helium-like systems.Moreover,the symmetric base functions for L=1,and analytic expressions of the related matrix elements are also given.
Masss pectrometry and electron diffraction were used to analyze the mass fractionation and profile of binary mixed supersonic jets generated from a Lavel nozzle.Mass spectrometry shows the advantage of determining both the profile of the jet and mass fraction ationinside the jet,while electron diffraction can provide the information about the jet profile and which solid phase is forme din the jet.
Twenty-six P10 models were acquired with molecular graphics and then carried out the optimizations with molecular mechanics,PM3 semi-empirical and ab intio calculations.The phosphourus atoms could be in one-fold,two-fold,three-fold and four-fold in these models.Most of models are designed by adding one or two atoms in the P8 and P9 clusters.Fifteen models having local minimum on the potential-energy surface are showed.Eleven models(the saddle point or the transitive state)having negative eigenvalue also be displayed.From comparing the total energies of the different models,the structures derived from the tetrahedral P4 by connecting P2 with four single bonds are favor in the total energy.Many models can be derived from cuneane P8 by adding two two-fold atoms,one of them is quite stable also.The tetrahedral P4 and the cuneane P8 Play the important roles in the compositions of the large phosphorus clusters.A special structure containing two one-fold atoms,two triple bond (1.95 ),was obtained after geometry optimization.The total energies of negative eigenvalue are normally higher than the local minimum.
It can be expressed as following equation for the change rule of the firstionization potential(Ip) of halohydrocarbonRX :Ip(eV)=3.3380+0.7344Ep(X)+2.7424(1/ax)qx-1.4302PEI where Ep(X) and ax are the ionization potential of outermost P electron and atomic polarizability for halogen atom respectively,qx is the partial charge on halogen atom X in halohydrocarbon molecule RX,and PEI is the polarizability effect index of alkyl group in the molecule RX.The result shown there were good agreement between the ionization potential values estimatedn by above expression and the experimental values for the investigated halohydrocarbon.
This paper provides a molecular dynamics simulation of nanocrystal of silver using a many-body potential in the frame-work of the Local-Density Approximation(LDA) and Second-Moment Approximation(SMA) to the tight-binding theory.In order to obtain the necessary parameters,we fit the total energy obtained fromm augmented-plane-wave calculations as a function of volume.We apply this scheme to calculate the equilibrium lattice constants,binding energy,free energy,relaxed surface energy,bulk modules,elastic constants and melting temperature.To cheak the accuracy of this method we evaluate structural energies,elasticenergy,and melting temperature etc.Our results are in more agreement with experiments than other methods.
Several aromatic amine compounds E-12,E-13,E-14,and E-15 are all organic electroluminescent(EL)and photoluminescent(PL)materials with good characteristics.Quantum chemistry calculations have been made.Their geometric configurations have been optimized by RHF/AM1.Their electronic spectra have been calculated by RHF/CIS.The calculated results are essentially consistent with experimental values.
Characteristic on the tangent of dielectric loss angle for coal has been researched by using fractal geometry theory.The results show that the tangent of dielectric loss angle of coal has fractal characteristic,relationship between and frequency is:tg**f(D-d)/2,and fractal dimension of tg* for coal could be obtained.
Ab initio molecular method is used to theoretically investigate the interactions of water with theCu(100)and Al(111)surface.Cu5,Al4 and Al10 clusters are used to simulate the different kinds of surfaces.At different basis set level of H2O in adsorption system,the potential energy surface of the HOH plane tilted of three systems are calculated.Without consideration of the d orbitals of the oxygenatom,the optimized structure is the water plane normal to the surface,and the H2Otilting of40o~50 ois found to require smallamount of energy.When the d orbitals of oxygen atom aetaken into account,the calculated structure of adsorbed H2O monomer with an inclined molecular axis such as Cu50o,Al40o is in an agreement with experimental results.The results indicate that the d orbitals of oxygena tom have the critical effect on the structure of the adsorbed H2O monomer.
Two new saponins containing five sugars have been isolated from the ethanol extract of the root of Dipsocus japonicus and their structures established as(3-O-α-L-rhammopyranosyl(1→3)- α-D-glycopyranosyl(1→3)-α-L-rhammopyranosyl(1→2)-α-L-arabinopyranosyl-hederagenin-28-O-α-D-glycopranoside(1)and3-O-α-D--glycopyranosyl(1→4)] α-L-rhamnopyranosyl(1→3)]- α-D-glycopyranosyl(1→3)- α-L[WTBZ]-rhamnopyranosyl(1→2)- α-L-arabinopyranosyl-oleanoic acid(2).Two new NMR techniques,1D-SEMDY and NOE difference spectroscopy in rotating frame have been successfully used to determine the chemical structure of oligosaccharide chains of the saponins.The results obtained showed that the sites of glycosylation and the sequence of sugars in the saponins can be determined unambiguously and total assignment of severely overlapping pro~ton resonance of sugar residues were achieved,without having recourse to chemical degration or modification.
The porous silicon (PS) samples were prepared by anodic etching method,and the Er3+,In3+were implanted into the PS samples by plating method.The results show that the implantation of such ions improves greatly the intensity of photoluminescence(PL) of the PS samples and makes the PL peak slightly blue-shift.With the increase of the plating time,the intensity of the PL increases continuously,but it has a saturation property to the plating time.
Segmented carbon filaments were prepared by pyrolysis of acetylene using foam Ni as the catalyst.The effects of reaction conditions on the yield and the morphology of the product were studied.The growth mechanism of the sample is discussed.It is suggested that the different micro-crystal faces of the catalyst favor either the adsorption and dissociation of gaseous hydrocarbon or the carbon deposition respectively.So the original shapes of the catalyst grains have affected the product morphology.
The effect of ZrO2 additives on Rh/γ-Al2O3 was studied.The TPR,XRD,BET surface area and the catalysts activity of NO+C2H4 and NO+C2H4+O2 reactions were measured for the catalysts with variety of crystal phases and doping manners of ZrO2 It is found that the ZrO2 possesses the ability of depressing the interaction between Rh3+ and γ-Al2O3 and retarding the phase transition of γ-Al2O3 to some extent.The reaction activity of NO+C2H4 is pronounced enhanced during ZrO2 doped onto the Rh/γ-Al2O3 after aging at 850℃ in atmosphere for 2h than that of the Rh/γ-Al2O3,while the activity of SCR for the samples is low and the sample containing ZrO2 is lower than that of the Rh/γ-Al2O3.It implicates that the reaction mechanism is quite different between NO+C2H4 and NO+C2H4+O2.The Competitive full oxidation of C2H4 promoting by ZrO2 is suggested.
Ultrafine titania particles were prepared by gas-phase oxidation of titanium tetrachloride in a high temperature tubular gas-phase reactor.The homogeneous precipitation method was used to prepare SnO2-TiO2 composite particles.The composite particles were characterized by TEM,EDS,XRD and BET surface area.The synthesized composite particles,pure ultrafine TiO2,commercial TiO2,and pure SnO2 were employed for photocatalytic degradation of azo dye active red X-3B in aerated solution.The result showed that a rapid and decolorization of the azo dye was achieved,and the photoactivity of the composite particles was higher than that of the pure ultrafine TiO2 and commercial TiO2,and the optimum loading of SnO2 on TiO2 is 15.3%.The enhanced degradation rate of X-3B using SnO2-TiO2 composite particles was attributed to increased charge separation in these systems.
The efficacy of a template can be rationalized in terms of the energies of the host-template nonbonding interactions.This approach is used to investigate the relationship between zeolite products and the diquat template molecules in their synthesis.The systematic syn~thesis results,especially the diquat chain length dependence of the products,ZSM-23,ZSM-50,NU-87,and ZSM-12 are rationalized quantitatively.
Filled clusters of cobalt-phthalocyanine/Iron nanoparticles have been obtained using method of organic-inorganic composite in situ with cobalt-phthalocyanine(CoPc) and carbonyl iron.The filled clusters consist of α-Fe nanoparticles in the inner of the nanocomposite particle and interface of CoPc layers.And interface of theα-Fe nanoparticles and surface of the clusters are completely covered by CoPc layers.Diameters of the-α Fe nanoparticles are ranged from 10nm to 15nm.And average diameter of the clusters was 1.4μm including thickness of CoPc layers from 50 to 150nm.For the filled clusters,the density is 3.664g/cm3,the saturatation intensity of magnetization is 76.3Am2/kg,and the coercive force is 4.15kA/m.Thermal stability of the filled clusters is excess of 150℃。There is a long-term stability of anti-sedimentation for the magnetorheological suspension consisting of the filled clusters and methylic silicone oil.
The paper reports the preparation and the gas-sensing properties of Y1-xMgxFeO3 prepared by chemical co-precipitation method.Y2O3,Fe(NO3)3·H2O,Mg(NO3)2and HNO3· were used as starting materials.Y2O3 was dissolved in HNO3 and mixed with Fe(NO3)3 and Mg(NO3)2 solution according to intended ratio,the(NH4)2CO3 solution was dropped into the mixed solution to make Fe3+,Mg2+and Y3+ coprecipitate.The coprecipitate were washed by distilled water,filtered,dried at 100℃,milled and calcined at 900℃for 4h Mg2+ doping decreases the lattice constants and size of the material.Whenx≤0.8,the curie temperature of Y1-xMgxFeO3 is 100℃than that of YFeO3 and the conductivity of the sensor based on Y1-xMgxFeO3 is higher than that of the sensor based on YFeO3.The reason forit is that Mg2+dopingm forms many holes which can be indicated by the equation:Mg[WTBX]Y*→MgY'+h.The sensitivity to C2H5OH of the sensor based on Y1-xMgxFeO3 is higher than that of sensor based on YFeO3,but the sensitivity to other gases of the sensor based on Y1-xMgxFeO3 is almost equal to that of sensor based on YFeO3 which may be because Mg2+play a catalytic role in the reaction of C2H5OH oxidation.The sensor based on Y0.94Mg0.06FeO3 exhibits highest sensitivity to C2H5OH at 257℃,and S4.5*mol/LC2H5OH/S45*mol/Lpetrol≈4.0.It is a promising gas-sensing material.
The effect of amount of emulsifier on the seeded emulsion polymerization was given in detail.Copolymer nanospheres of styrene/acrylic acid were prepared.In addition,the preparation of copolymer core magnetite shell composite particles were, reported.These composite particles were characterized by XRD and TEM.In this paper,a suspension with these composite particles dispersed was also prepared.Its suspension properties and viscosity variation with the applied magnetic field were further studied.
The capability of lateral dissipating static charge characterizes the electrical properties of a fabric softener that can be absorbed on fabric surfaces as mono-layer or multi-layers after washing.The DDAC LB multi-layers have been deposited onto thin polyester substrates.Under different relative humidities,the lateral conductance have been measured and non-liner results have been obtained.The atomic force microscopy(AFM)images show non-uniformity of DDAC multi-layers which may result in the non-liner relationships between lateral conductance and relative humidities(RH)ambient.Based on the data of current and voltage applied,the sheet resistance of deposited DDAC films have been calculated.Percolation theory and patch-overlapping models at different RH have been employed to interpret these non-linear relationships for DDAC multi-layers.It has been found out that the current flowing through the multilayers is controlled by relative humidities and the relationship between the thickness of the multilayers and the RH also does great contribution to the lateral conductance.Based on these,a theoretical explanation and analysis have been given.
The thermally stimulated current(TSC)behaviors of PT/P[VDF(70)-TrFE(30)]composite were investigated systematically.Two kinds of the ferroelectric phase(less organized ferroelectric and organized ferroelectric phase)coexist in the copolymer matrix at room temperature.The phase transitions can be identified clearly by poling sample above the Curie point and then cooling it to different temperatures.The result shows that the para-to-ferroelec trictransitions on cooling appear at 62℃and 50℃,and ferro-to-paraelectric transitions on heating at about 95℃ and 108℃,respectively.It also indicates that traps exist in ferroelectric phase but not in paraelectric phase of the copolymer.Lead titanate(PT) does not contribute to the current peaks within the experimental temperature range,but it makes Tc decrease and causes the current density increase compared with the pure copolymer.
A series of magnetoplumbite oxides CaNiyAl12-yO19-δ(y=0.3,0.6,0.9,1.0)were prepared and characterized using XRD,XPS,TPR and TGA techniques.The results showed that the series of oxides CaNiyAl12-yO19-δexhibited almost the same crystal structure and similar reduction stability.A pure magnetoplumbite oxidesCaNiyAl12-yO19-δ phase could be formed only when y value is at 0
The surface tension of liquid nitrogen at 77 K is measured to be 9.053 dyn/cm in terms of the double capillary method,which may be reasonable in comparison with the single capillary method.The nonlinear equation *=*0(1-T/TC)n has been used to describe the relation between the surface tension with the temperature for liquefied N2,O2,Ar,Xe,H2,Ne,He,F2,D2 and Kr.The parameters *0 and n of the liquefied gases above are fitted by the linear regression method with higher accuracy than that in the literatures.