Effects of self energy of the ions on the double layer structure and properties at the dielectric interface

Although numerous theoretical efforts have been put forth, a systematic, unified and predictive theoretical framework that is able to capture all the essential physics of the interfacial behaviors of ions, such as the Hofmeister series effect, Jones-Ray effect and the salt effect on the bubble coalescence remain an outstanding challenge. The most common approach to treating electrostatic interactions in the presence of salt ions is the Poisson-Boltzmann (PB) theory. However, there are many systems for which the PB theory fails to offer even a qualitative explanation of the behavior, especially for ions distributed in the vicinity of an interface with dielectric contrast between the two media (like the water-vapor/oil interface). A key factor missing in the PB theory is the self energy of the ion.

In this thesis, we develop a self-consistent theory that treats the electrostatic self energy (including both the short-range Born solvation energy and the long-range image charge interactions), the nonelectrostatic contribution of the self energy, the ion-ion correlation and the screening effect systematically in a single framework. By assuming a finite charge spread of the ion instead of using the point-charge model, the self energy obtained by our theory is free of the divergence problems and gives a continuous self energy across the interface. This continuous feature allows ions on the water side and the vapor/oil side of the interface to be treated in a unified framework. The theory involves a minimum set of parameters of the ion, such as the valency, radius, polarizability of the ions, and the dielectric constants of the medium, that are both intrinsic and readily available. The general theory is first applied to study the thermodynamic property of the bulk electrolyte solution, which shows good agreement with the experiment result for predicting the activity coefficient and osmotic coefficient.

Next, we address the effect of local Born solvation energy on the bulk thermodynamics and interfacial properties of electrolyte solution mixtures. We show that difference in the solvation energy between the cations and anions naturally gives rise to local charge separation near the interface, and a finite Galvani potential between two coexisting solutions. The miscibility of the mixture can either increases or decreases depending on the competition between the solvation energy and translation entropy of the ions. The interfacial tension shows a non-monotonic dependence on the salt concentration: it increases linearly with the salt concentration at higher concentrations, and decreases approximately as the square root of the salt concentration for dilute solutions, which is in agreement with the Jones-Ray effect observed in experiment.

Next, we investigate the image effects on the double layer structure and interfacial properties near a single charged plate. We show that the image charge repulsion creates a depletion boundary layer that cannot be captured by a regular perturbation approach. The correct weak-coupling theory must include the self-energy of the ion due to the image charge interaction. The image force qualitatively alters the double layer structure and properties, and gives rise to many non-PB effects, such as nonmonotonic dependence of the surface energy on concentration and charge inversion. The image charge effect is then studied for electrolyte solutions between two plates. For two neutral plates, we show that depletion of the salt ions by the image charge repulsion results in short-range attractive and long-range repulsive forces. If cations and anions are of different valency, the asymmetric depletion leads to the formation of an induced electrical double layer. For two charged plates, the competition between the surface charge and the image charge effect can give rise to like- charge attraction.

Then, we study the inhomogeneous screening effect near the dielectric interface due to the anisotropic and nonuniform ion distribution. We show that the double layer structure and interfacial properties is drastically affected by the inhomogeneous screening if the bulk Debye screening length is comparable or smaller than the Bjerrum length. The width of the depletion layer is characterized by the Bjerrum length, independent of the salt concentration. We predict that the negative adsorption of ions at the interface increases linearly with the salt concentration, which cannot be captured by either the bulk screening approximation or the WKB approximation. For asymmetric salt, the inhomogeneous screening enhances the charge separation in the induced double layer and significantly increases the value of the surface potential.

Finally, to account for the ion specificity, we study the self energy of a single ion across the dielectric interface. The ion is considered to be polarizable: its charge distribution can be self-adjusted to the local dielectric environment to minimize the self energy. Using intrinsic parameters of the ions, such as the valency, radius, and polarizability, we predict the specific ion effect on the interfacial affinity of halogen anions at the water/air interface, and the strong adsorption of hydrophobic ions at the water/oil interface, in agreement with experiments and atomistic simulations.

The theory developed in this work represents the most systematic theoretical technique for weak-coupling electrolytes. We expect the theory to be more useful for studying a wide range of structural and dynamic properties in physicochemical, colloidal, soft-matter and biophysical systems.

Low-loss planar and stripe waveguides in Nd3+-doped silicate glass produced by oxygen-ion implantation

We report on the fabrication and characterization of low-loss planar and stripe waveguides in a Nd3+-doped glass by 6 MeV oxygen-ion implantation at a dose of 1x10(15) ions/cm(2). The dark mode spectroscopy of the planar waveguide was measured using a prism coupling arrangement. The refractive index profile of the planar waveguide was reconstructed from a code based on the reflectivity calculation method. The results indicate that a refractive index enhanced region as well as an optical barrier have been created after the ion beam processing. The near-field mode profiles of the stripe waveguide were obtained by an end-fire coupling arrangement, by which three quasitransverse electric modes were observed. After annealing, the propagation losses of the planar and stripe waveguides were reduced to be similar to 0.5 and similar to 1.8 dB/cm, respectively. (c) 2007 American Institute of Physics.

Mode control in vertical-cavity surface-emitting lasers by post-processing using focused ion-beaih etching

Single-mode emission is achieved in previously multimode gain-guided vertical-cavity surface-emitting lasers (VCSEL's) by localized modification of the mirror reflectivity using focused ion-beam etching. Reflectivity engineering is also demonstrated to suppress transverse mode emission in an oxide-confined device, reducing the spectral width from 1.2 nm to less than 0.5 nm.

Diamond nucleation by energetic pure carbon bombardment

Deposition of 1000 eV pure carbon ions onto Si(001) held at 800 degrees C led to direct nucleation of diamond crystallites, as proven by high-resolution transmission electron microscopy and electron energy loss spectroscopy. Molecular dynamic simulations show that diamond nucleation in the absence of hydrogen can occur by precipitation of diamond clusters in a dense amorphous carbon matrix generated by subplantation. Once the diamond clusters are formed, they can grow by thermal annealing consuming carbon atoms from the amorphous matrix. The results are applicable to other materials as well.

Determination of the interdiffusion coefficients of liquid Zn and Sn using Ta/Zn-Sn/Si trilayers

In this paper we present a new method for measuring diffusion coefficients in liquid metals under convection-less conditions with solid/liquid-liquid/solid trilayer. The advantage of this kind of trilayer is that effects from gravity-induced convection and Marangoni-convection can be omitted, so that the diffusion coefficient is determined more accurately. The Ta/Zn-Sn/Si trilayer were prepared with a multi-target ion-beam sputtering deposition technique and annealed in an electric furnace under an argon atmosphere. The interdiffusion of liquid zinc and tin at 500 degrees degree C was investigated. The diffusion concentration profiles were determined by energy dispersive spectroscopy. The interdiffusion coefficients range from 1.0x10(-6)cm(2)/s to 2.8x10(-6)cm(2)/s, which is less than previous values measured by capillary reservoir technique under 1g-environment where various convection exist. The precise interdiffusion coefficients of liquid zinc and tin result from the removing of disturbances of various kinds of convection.

Domains in ferroelectric nanodots

Almost free-standing single crystal mesoscale and nanoscale dots of ferroelectric BaTiO(3) have been made by direct focused ion beam patterning of bulk single crystal material. The domain structures which appear in these single crystal dots, after cooling through the Curie temperature, were observed to form into quadrants, with each quadrant consisting of fine 90 degrees stripe domains. The reason that these rather complex domain configurations form is uncertain, but we consider and discuss three possibilities for their genesis: first, that the quadrant features initially form to facilitate field-closure, but then develop 90 degrees shape compensating stripe domains in order to accommodate disclination stresses; second, that they are the result of the impingement of domain packets which nucleate at the sidewalls of the dots forming "Forsbergh" patterns (essentially the result of phase transition kinetics); and third, that 90 degrees domains form to conserve the shape of the nanodot as it is cooled through the Curie temperature but arrange into quadrant packets in order to minimize the energy associated with uncompensated surface charges (thus representing an equilibrium state). While the third model is the preferred one, we note that the second and third models are not mutually exclusive.

INVESTIGATION OF BURIED ALN LAYERS FORMED BY NITROGEN IMPLANTATION INTO AL

The composition and microstructure of buried layers of AlN formed by high energy N+ ion implantation into polycrystalline Al have been determined. Both bulk and evaporated thin films of Al have been implanted with 100 and 200 keV N+ ions to doses of up to 1.8 x 10(18)/cm2. The layers have been characterised using SIMS, XTEM, X-ray diffraction, FTIR, RBS and in terms of their microhardness. It is found that, for doses greater than the critical dose, buried, polycrystalline AlN layers are formed with preferred (100) or (002) orientations, which are sample specific. With increasing dose the nitrogen concentration saturates at the value for stoichiometric AlN although the synthesised compound is found to be rich in oxygen.

Nano-layer structure of silicon-on-insulator materials

Silicon-on-insulator (SOI) has been recognized as a promising semiconductor starting material for ICs where high speed and low power consumption are desirable, in addition to its unique applications in radiation-hardened circuits. In the present paper, three novel SOI nano-layer structures have been demonstrated. ULTRA-THIN SOI has been fabricated by separation by implantation of oxygen (SIMOX) technique at low oxygen ion energy of 45 keV and implantation dosage of 1.81017/cm2. The formed SOI layer is uniform with thickness of only 60 nm. This layer is of crystalline quality. and the interface between this layer and the buried oxide layer is very sharp, PATTERNED SOI nanostructure is illustrated by source and drain on insulator (DSOI) MOSFETs. The DSOI structure has been formed by selective oxygen ion implantation in SIMOX process. With the patterned SOI technology, the floating-body effect and self-heating effect, which occur in the conventional SOI devices, are significantly suppressed. In order to improve the total-dose irradiation hardness of SOI devices, SILICON ON INSULATING MULTILAYERS (SOIM) nano-structure is proposed. The buried insulating multilayers, which are composed of SiOx and SiNy layers, have been realized by implantation of nitride and oxygen ions into silicon in turn at different ion energies, followed by two steps of high temperature annealing process, respectively, Electric property investigation shows that the hardness to the total-dose irradiation of SOIM is remarkably superior to those of the conventional SIMOX SOI and the Bond-and-Etch-Back SOI.

Determination of the interdiffusion coefficients of liquid Zn and Sn using Ta/Zn-Sn/Si trilayers

In this paper we present a new method for measuring diffusion coefficients in liquid metals under convection-less conditions with solid/liquid-liquid/solid trilayer. The advantage of this kind of trilayer is that effects from gravity-induced convection and Marangoni-convection can be omitted, so that the diffusion coefficient is determined more accurately. The Ta/Zn-Sn/Si trilayer were prepared with a multi-target ion-beam sputtering deposition technique and annealed in an electric furnace under an argon atmosphere. The interdiffusion of liquid zinc and tin at 500 degrees degree C was investigated. The diffusion concentration profiles were determined by energy dispersive spectroscopy. The interdiffusion coefficients range from 1.0x10(-6)cm(2)/s to 2.8x10(-6)cm(2)/s, which is less than previous values measured by capillary reservoir technique under 1g-environment where various convection exist. The precise interdiffusion coefficients of liquid zinc and tin result from the removing of disturbances of various kinds of convection.

中能重离子在位置灵敏CsI（Tl)探测器中能损与光输出响应的关系

In this paper, we describe the structure and readout system of a two-dimension positional sensitive CsI(Tl) detector, and investigates the relation between energy lose and light output of the CsI(Tl) detector with secondary beams in intermediate energy.Bρ+(ΔE-TOF) method was used to distinguish the secondary beam.Linearity of the position signals of the CsI(Tl) was corrected.Energy signals from the CsI(Tl) detector were calibrated using the relationship of the Z, A and the light output response of the incid...中文摘要：描述了一种双维位置灵敏CsI(Tl)探测器的结构及其读出系统,用中能次级束研究其能损与光输出关系。使用Bρ+(ΔE-TOF)方法鉴别次级束,刻度了CsI(Tl)探测器位置信号的线性,并用其光输出与入射粒子的A、Z关系刻度其能量。结果表明,CsI(Tl)探测器输出信号的ADC读出与QDC读出(即其光输出)有很好的线性关系。

Adenovirus-mediated wild-type P53 Transfer radiosensitizes H1299 cells to subclinical-dose carbon-ion irradiation through the restoration of p53 function

To determine whether adenovirus-mediated wild-type p53 transfer after radiotherapy could radiosensitize non-small-cell lung cancer (NSCLC) cells to subclinical-dose carbon-ion beam (C-beam), H1299 cells were exposed to a C-beam or -ray and then infected with 5 MOI of AdCMV-p53 or GFP (C-beam or -ray with p53 or GFP).Cell cycle was detected by flow cytometric analysis. The apoptosis was examined by a fluorescent microscope with DAPI staining. DNA fragmentation was monitored by the TUNEL assay. P53 mRNA was detected by reverse-transcriptase polymerase chain reaction. The expression of p53, MDM2, and p21 was monitored by Western blot. Survival fractions were determined by colony-forming assay. The percentages of G1-phase cells in C-beam with p53 increased by 8.2%–16.0%, 5.2%–7.0%, and 5.8%–18.9%, respectively, compared with C-beam only, -ray with p53, or p53 only. The accumulation of G2-phase cells in C-beam with p53 increased by 5.7%–8.9% and 8.8%–14.8%, compared with those in -ray with p53 or p53 only, respectively. The percentage of apoptosis for C-beam with p53 increased by 7.4%–19.1%, 5.8%–11.7%, and 5.2%–19.2%, respectively, compared with C-beam only, -ray with p53, or p53 only. The level of p53 mRNA in C-beam with p53 was significantly higher than that in p53 only. The expression level of p53 and p21 in C-beam with p53 was significantly higher than that in both C-beam with GFP and p53 only. The survival fractions for C-beam with p53 were significantly less than those for the other groups (p 0.05). The data suggested that AdCMV-p53 transfer could more efficiently radiosensitize H1299 cells to subclinical-dose C-beam irradiation through the restoration of p53 function.

Experimental verification of therapeutic doses for the superficially-placed tumor radiotherapy with heavy ions at HIRFL

Up to now, clinical trials of heavy-ion radiotherapy for superficially placed tumors have been carried out for six times and over 60 selected patients have been treated with 80—100 MeV/u carbon ions supplied by the Heavy Ion Research Facility in Lanzhou (HIRFL) at the Institute of Modern Physics, Chinese Academy of Sciences since November, 2006. A passive irradiation system and a dose optimization method for radiotherapy with carbon-ion beams have been developed. Experimental verification of longitudinally ...

Investigation of excited states in 22Mg via resonant elastic scattering of 21Na+p and its astrophysical implications

The excited states in 22Mg have been investigated by the resonant elastic scattering of 21Na + p.A 4.0 MeV/nucleon 21Na beam was separated by the Center for Nuclear Study (CNS) radioactive ion beam separator (CRIB) and then used to bombard a thick (CH2)n target. The energy spectra of recoiled protons were measured at scattering angles of θc.m. ≈ 172◦, 146◦, and 134◦, respectively. A wide energy-range of excitation function in 22Mg (up to Ex ∼ 8.9 MeV) was obtained simultaneously with a thick-target method, and a state at 7.06 MeV was newly observed. The resonant parameters were deduced from an R-matrix analysis of the center-of-mass (c.m.) differential cross-section data with a SAMMY-M6-BETA code. The astrophysical resonant reaction rate for the 18Ne(α,p)21Na reactionwas recalculated based on the present parameters.Generally speaking,the present rates are much smaller than the previous ones.

HIRFL-CSR频谱现象：中心频率突变分析研究

In commissioning the HIRFL-CSR (Cooler Storage Ring of Heavy Ion Research Facility in Lanzhou),with the spectrum analyzer monitoring the beams on-line, we measured many parameters of the beam status for improving quality of the heavy ion beams. In this paper, the sudden change of the beam center frequency is analyzed.A theoretical analysis is done mainly on instabilities of the electron voltage and the neutralization factor. Simulations were made for the problem. According to the simulation result, we can conclude that it is the instability of neutralization factor that caused the problem. 中文摘要：HIRFL-CSR调试过程中，利用频谱分析仪实时监测束流，根据其上测的数据进行相关参数调整，改善束流的品质。本文对分析仪上观测到的现象一束流的中心频率发生突变进行了研究，主要就电子束的高压不稳定性和中性化因子的突变做了理论分析，并进行了相关的模拟计算 ，根据模拟结果初步断定该现象的出现由电子束的中性化因子导致。

全永磁ECR离子源研究进展

Electron Cyclotron Resonance (ECR) ion source is regarded as the most efficient machine to produce stable multiple charge state ion beams. Because of the special characteristics, all-permanent magnet ECR ion sources have been widely adopted around the world to produce stable ion beams of multiple charge state with good repetition have been widely adopted around the world to produce stable ion beams of multiple charge state with good repetition and high duty factor for compact research platforms and ion beam implanters. In this paper, all-permanent magnet ECR ion sources developed at IMP are presented, and typical parameters and performances are discussed. The high charge state source, LAPECR2, is mainly used to produce intense high charge state ion beams, and the LAPECR1 source is designed to produce intense ion beams of medium and low charge state. An improved LAPECR1-M is specially designed to produce heavy metal ion beams of low charge state. These ECR ion sources have been adopted by different experimental terminals at IMP and, with their nice performance, many experimental studies could be possible. 中文文摘：ECR(电子回旋共振)离子源是产生稳定的强流多电荷态离子束流最有效装置。全永磁ECR 离子源因其独特的特点为很多中小型多电荷态离子束流实验平台与离子注入机等系统所采用，为后者产生重复性好、稳定性强的多电荷态离子束流。本文着重论述了中国科学院近代物理研究所研制的几台全永磁多电荷态ECR 离子源及其特性与典型性能，如能产生强流高电荷态离子束流的高性能全永磁离子源LAPECR2，能产生强流中 低电荷态离子束流的LAPECR1，能产生多电荷态重金属离子束流的LAPECR1-M 等。这些性能稳定的离子源为提高近代物理研究所相关试验平台的性能提供了关键的束流品质保障。