SPECTRAL VARIATION AND CHARACTERISTICS OF LOW VALENCY RARE EARTH IONS IN COMPLEX OXIDESⅢ.EFFECT OF THE CRYSTAL ENVIRONMENT AND CHEMICAL FACTORS ON LUMINESCENCE PROPERTIES OF EUROPIUM (Ⅱ) ION

In this paper,the influence of crystal-field on the Luminescence properties of Eu^(2+) in complex oxides are studied theoretically by using purely electrostatic model,the dependence of the 4f^65d levels on Eu-O bond distance is given.Quantum chemistry calculation shows that the splitting extent of 4f^65d energy band in cubic or in octahedral fields will be inversely proportional to R^5,where R is the distance of Eu^(2+) to oxygen ligand.The value of R affects slightly the location of the centre of 4f^65d energy band.According to the exper- imental spectrum data,we have discussed the influence of the host chemical composition,the replaced sites of Eu^(2+) and degree of covalency of Eu-O bond on luminescence properties of Eu^(2+).Some regularity of fluorescence spectrum was observed. In alkali-alkaline earth-phosphates,the splitting extent of 4f^65d band (△E) becomes smaller as the Eu-O bond distance (R) increases.In Na_(3-x)(PO_4)_(1-x)(SO_4)_x and Na_(2-x)CaSi_(1-x)P_xO_4 hosts,d-d emission peak of Eu^(2+) will shift to shorter wavelength with the increase of x's value. The crystal structure data show that Eu^(2+) in K_2Mg_2(SO_4)_3 is affected more strongly by crystal-field and covalancy than in KMgF_3,so K_2Mg_2(SO_4)_3:Eu^(2+) emits blue light (E_(em)~m=400nm) and KMgF_3:Eu^(2+) produces ultraviolet fluorescence.

Characteristics of Resistance Triggering of a Pulsed Vacuum Arc Ion Source

Triggering scheme is a significant factor that may influence the process of vacuum arc initiation. In this work, the characteristics of resistance triggering of a pulsed vacuum arc ion source are investigated and compared with the independent pulse generator triggering. The results show that although the resistance triggering method is capable of triggering a vacuum arc ion source by properly choosing the resistance and electric parameters, it inevitably increases the rise time of the arc current. A high speed multiframe camera is used to reveal the transition process o~ arc initiation during one shot. From the images it is conjectured that the lower voltage between the cathode and the anode may be the reason that leads to the lower transition speed of discharge at the moment of arc initiation.

Plasma characteristics in the discharge region of a 20A emission current hollow cathode

Numerical calculation and fluid simulation methods were used to obtain the plasma characteristics in the discharge region of the LIPS-300 ion thruster’s 20 A emission current hollow cathode and to verify the structural design of the emitter.The results of the two methods indicated that the highest plasma density and electron temperature,which improved significantly in the orifice region,were located in the discharge region of the hollow cathode.The magnitude of plasma density was about 10^21m^-3in the emitter and orifice regions,as obtained by numerical calculations,but decreased exponentially in the plume region with the distance from the orifice exit.Meanwhile,compared to the emitter region,the electron temperature and current improved by about 36%in the orifice region.The hollow cathode performance test results were in good agreement with the numerical calculation results,which proved that that the structural design of the emitter and the orifice met the requirements of a 20 A emission current.The numerical calculation method can be used to estimate plasma characteristics in the preliminary design stage of hollow cathodes.

Effects of Boundary Current on Electromagnetic Dispersion Characteristics for a Relativistic Electron Beam

With betatron oscillation characteristics of the electron beam and ion channel effect taken into account,dispersion characteristics of electrostatic modes and TM modes for a relativistic electron beam guided by ion channel are studied.Dispersion relations are derived and solved numerically to investigate the dependence of the dispersion characteristics for electrostatic modes and TM modes on the betatron oscillation frequency and the ratio of the relativistic electron beam radius to the waveguide radius.The effects of the boundary current on the dispersion characteristic of the TM modes and the interaction between the betatron modes and TM modes are analyzed.When considering the boundary current,for a strong ion channel,a new low-frequency branch of the TM modes arises and the interaction frequency between the betatron modes and the TM01modes is increased with the same parameters.

Comparison of the removal of monovalent and divalent cations in the microbial desalination cell

Microbial desalination cell （MDC） is a promis- ing technology to desalinate water and generate electrical power simultaneously. The objectives of this study were to investigate the desalination performance of monovalent and divalent cations in the MDC, and discuss the effect of ion characteristics, ion concentrations, and electrical characteristics. Mixed salt solutions of NaC1, MgC12, KC1, and CaC12 with the same concentration were used in the desalination chamber to study removal of cations. Results showed that in the mixed salt solutions, the electrodialysis desalination rates of cations were： Ca2＋ 〉 Mg2＋ 〉 Na＋ 〉 K＋. Higher ionic charges and smaller hydrated ionic radii resulted in higher desalination rates of the cations, in which the ionic charge was more important than the hydrated ionic radius. Mixed solutions of NaC1 and MgC12 with different concentrations were used in the desalination chamber to study the effect of ion concentra- tions. Results showed that when ion concentrations ofNa＋ were one-fifth to five times of Mg2~, ion concentration influenced the dialysis more profoundly than electrodia- lysis. With the current densities below a certain value, charge transfer efficiencies became very low and the dialysis was the main process responsible for the desalination. And the phosphate transfer from the anode chamber and potassium transfer from the cathode chamber could balance 1%-3% of the charge transfer in the MDC.

A STUDY ABOUT SOIL WATER CHARACTERISTIC,CONDUCTIVITY OF WATER AND EQUILIBRIUM ADSORPTION OF CUPRIC ION IN SOIL——A UTILITY EQUIPMENT USED IN SOIL SCIENCE AND ITS ILLUSTRATION OF USE

A utility equipment used in soil science is designed and installed.The equipment can be used in research pro- grams of soil water and solute transport.Pressure in pressure chamber of the equipment in which a tested soil sam- ple is laid can be adjusted exactly so that we can determine the water content of soil sample.With the equipment we can not only study the problems related water movement in soil but also measure some solute,such as cadmi- um,plumbum and so on,adsorption on surface of soil in saturated and unsaturated state.As an illustration of the use of the equipment,we give the isothermal of cupric ion adsorption in soil.This equipment can be used in the re- search work and application of soil science.

A QICAR Model for Metal Ion Toxicity Established via PLS Method

The partial least squares（PLS） method was employed to establish a quantitative ion characteristics-activity relationship（QICAR） model for metal ion toxicity（EC50 of 15 metal ions）. The ion characteristics included AN（the atomic number）, AIP（the change in ionization potential, eV）, Xm（the electronegativity, eV）, AW（the atomic weight）, Xm2r（the covalent index）, △E0（the absolute difference between electrochemical potential of the ion and that of its first stable reduced state, eV）, ｜lgKoH｜ （the absolute value of the lg of the first hydrolysis constant）, AR（the atomic radius, nm）, AR/AW（the ratio between atomic radius and atomic weight） and ap（the softness index） selected based on relative correlation analysis. The simulated and tested（with the other four metals） efficiency coefficients of the model are 0.88 and 0.96, respectively. The information revealed from the QICAR model indicates that the value of the metal ion toxicity was positively correlated with variables AN, AlP, Xm, AW and Xm2r; negatively correlated with variables AE0, ｜IgKoH｜, AR/AW, AR and ap, and ion characteristics △E0, Xm, σp and Xm2r were found to contribute more to the toxicity of metal ions via the accurate analysis method provided by PLS. The model could be used to predict the toxicity of the target metals and preliminary to assess combined pollution and environmental risk for heavy metals in the environments.

Rearrangement reaction of the hydroxyl group of ω-hydroxy-alkyltriphenyl phosphonium bromides

No molecular ion peak from the Electron Impact lonization of eight co-hydroxyalkyltriphenyl phosphonium bromides(Ph3P+(CH2)nOHBr-,n=2-6,8-10)can be found,except a part of some relative powerful fragment ions can be observed only.Each compound forms a very characteristic ion(O=PPbj-1)+ at m/z 277 through hydroxyl rearrangement reaction.The intensity of this ion is closely related with the size of the carbon chain of hydroxyalkyl and with temperature of ion source and temperature of sample probe.The above rearrangement reaction and the reaction to form ion at m/z 262 take place simultaneously,thus leading to strong competition.At n=2,ion at m/z 277 is the most powerful and becomes continuously the base peak.At n=3 and n=4,the intensity of ion at m/z 262 reaches the maximum,and is always the base peak,and the relative abundance of m/z 277 is only around 2%.At n=5,6,8,9,10,m/z 277 becomes base peak when the temperature of probe is below 300℃.But,when the temperature increases from 300℃to 350℃,m/z 262 suddenly becomes the base peak,which is not in direct proportional relation with the size of carbon chain.It is proved by MIKES and accurate mass that ion at m/z 277 produces a fragment ion(O=PPh2-2)+ at m/z 199 with the loss of the neutral benzene molecule.