激光尾场第一周期加速带电粒子模拟

在关于激光尾场加速(LWFA)的很多文献中,都暗示了尾场有周期性结构.可是激光驱动尾场可以不是周期性的,尾场第一周期可以捕获和加速外来电子束.Esirkepov和Bulanov等人提出了带电粒子在激光高斯脉冲驱动尾场第一周期加速的处理方法.本文在此理论基础上进一步讨论电子在尾场第一周期中能获得的最大能量与激光脉冲的强度和脉冲的波长之间的关系.结果显示,捕获电子最大能量与脉冲激光强度成正比.适当的选择脉冲激光波长也直接影响到捕获电子的最大能量值.     

Real-space observation of local anisotropic correlation between buckled dimers on Si(100) induced by a bidentate adsorbed molecule

The anisotropic correlation between buckled dimers on Si(100) was investigated by scanning tunneling microscopy. A bidentate ligand molecule was used to pin two neighboring dimers at 300 K. The chemically pinned dimer induces antiferromagnetic interaction along the dimer rows. Observed results agree well with Monte-Carlo simulations semi-quantitatively.     

Photosubstitution reactions in potassium octacyanomolybdate(IV) and octacyanotungstate(IV) in the presence of 1,10-phenanthroline and 2,2-́bipyridyl

Substitution reactions take place following the photonic excitation of aqueous K₄M(CN)₈ (where M = Mo or W) in the presence of 1,10-phenanthroline and 2,2$\text{-}\text{?}$bipyridyl. Changes in absorbance with time show that the overall reaction is dependent on photochemical activation of potassium octacyanomolybdate(IV) and -tungstate(IV). The species [K₂Mo(CN)₄(OH)₂(phen)], [K₂W(CN)₄(OH)₂(phen)], [K₂Mo(CN)₄(OH)₂(bipy)] and [K₂W(CN)₄(OH)₂(bipy)] exist in solution. The final photosubstitution products [Mo(OH)₃(CN)(phen)₂] · 2H₂O], [Mo(OH)₃(CN)(bipy)₂] · 3H₂O, [W(OH)₃(CN)(phen)₂] · 2H₂O and [W(OH)₃(CN)(bipy)₂] · H₂O have been isolated in the solid state. Their IR spectra have been discussed. The quantum yield of the photosubstitution reactions has been determined and its variation with change of concentration of the complex as well as the H⁺ ion concentration has been studied.     

New congruences for $$\ell $$-regular partitions for $$\ell \in \{5,6,7,49\}$$∈{5,6,7,49}

We find several new congruences for \(\ell \)-regular partitions for \(\ell \in \{5,6,7,49\}\) and also find alternative proofs of the congruences for 10- and 20-regular partitions which were proved earlier by Carlson and Webb (Ramanujan J 33:329–337, 2014) by using the theory of modular forms. We use certain p-dissections of \((q;q)_{\infty }\), \(\psi (q)\), \((q;q)_{\infty }^3\) and \(\psi (q^2)(q;q)_{\infty }^2\).     

Competing forward and reversed chain reactions in one-dimensional molecular line growth on the Si(100)-(2 x 1)-H surface

To explore the role of competing forward and reversed chain reactions in the growth of a one-dimensional (1D) molecular line on the Si(100)-(2 x 1)-H surface, controlled experiments were performed with various alkene molecules by scanning tunneling microscopy (STM) at various temperatures. It was observed that the end dangling bond (DB) of a styrene line, fabricated by a chain reaction on the Si(100)-(2 x 1)-H surface at 300 K, initiated a reverse chain reaction at 400 K, leading to the complete disappearance of the styrene line with zero-order desorption kinetics (rate constant k = 1.17 x 10-2 s-1 at 400 K). In the case of 2,4-dimethylstyrene, the reversed chain reaction was observed even at 300 K. These results suggest that the appearance of a molecular line in an STM image is determined by the rates of competing forward and reversed chain reactions at a given temperature. As predicted, 1D lines formed by the DB-initiated chain reaction of 1-hexene and 1-heptene on Si(100)-(2 x 1)-H were observed at 180 K because of the reduced desorption rate, despite the fact that those molecules showed no line growth at 300 K. These results indicate that the scope of forming 1D molecular lines on the Si(100)-(2 x 1)-H surface with various alkenes is much wider than anticipated in previous studies.     

(RS)‐6‐Ethyl 2‐carboxy‐1,2,3,4‐tetra­hydro­azulene‐6‐carboxylate

The title compound, C₁₄H₁₆O₄, was obtained during the synthesis of 2,6‐disubstituted azulene derivatives. In the partially reduced azulene skeleton, the absence of a H atom at the ester substitutent position of the seven‐membered ring, as well as lengthened double bonds, indicate a conjugative stabilized system with two overlaid tautomers.     

Analysis of the Electrohydrodynamic Flow in a Symmetric System of Electrodes by the Method of Dynamic Current–Voltage Characteristics

We have solved the problem of injection-type through electrohydrodynamic (EHD) flow in a closed channel. We have considered a model of a liquid with four types of ions. It is shown that a through EHD flow without internal vortices in the electrode gap is formed for the ratio 2 : 1 of the initial injection current from the electrodes in the channel. The structure of the flow in different parts of the channel and the integral characteristics of the flow have been analyzed. It is shown that for a quadratic function of injection at the electrodes, the current–voltage characteristic of the flow is also quadratic.     

超强激光与等离子体靶相互作用中高能离子的定向发射

等离子体薄靶作为控制激光加热和产生高能粒子的驱动源在激光核聚变快点火方案中被广泛应用.本文用二维粒子模拟方法研究了超强超短脉冲激光与平板等离子体薄靶相互作用中产生的高能离子.模拟研究结果表明,在平板等离子体薄靶后表面所产生的高能离子的角分布较小,定向性好,能获得很高的能量.并且等离子体薄靶的形状对高能离子的产生和会聚有一定的影响.     

Extraction of iridium(IV) from hydrochloric acid media with crown ether in chloroform, and its determination by ICP–AES

A new method for the quantitative extraction and determination of trace amounts of iridium from hydrochloric acid media has been established based on the formation of an ion-association complex of iridium hexachloro anion IrCl₆ ^2– with dicyclohexyl-18-crown-6 (DC18C6) oxonium cation in chloroform, then determination by inductively coupled plasma atomic emission spectrometry (ICP–AES). The effect of various factors (solvent, acid concentration, crown ether, reagent concentration, shaking time, composition of the extracted species, foreign ions, etc.) on the extraction and back-extraction of iridium has been investigated. The procedure was used to determine traces of iridium in palladium chloride and rhodium chloride.