吡咯与HX(X=F,Cl,Br)分子间多种氢键的电子密度拓扑研究

采用密度泛函B3LYP/6-311＋＋G(d,p)方法, 对吡咯与HX (X＝F, Cl, Br)形成的经典氢键和π型氢键, 从其几何参数、电子密度的拓扑性质和电子积分等方面进行了研究. 在对π型氢键的讨论中我们将π电子与σ电子分离, 得到了π型氢键体系的π电子的密度等值线和拉普拉斯量等值线图以及各原子的π电子积分, 形象地说明了π型氢键的作用本质.     

High harmonic generation in a two-color field composed of a pump field and a weak subsidiary high frequency field

“Coherent control of high-harmonic generation in a two-color field” has been widely concerned. Using split-operator algorithm, we have calculated the high-harmonic generation for helium ion He+ in a two-color field which is composed of a driving field and a weak subsidiary high frequency field (Is=I0/100, （ω,13ω), …(ω, 120ω)) and found that such a field can produce much higher harmonic intensity, typically increasing the harmonics corresponding to the incident frequency of the subsidiary field. The different effects coming from the different subsidiary fields are calculated and analyzed. It is indicated that one of the important underlying mechanisms is high frequency photon induced radiation.     

PREPARATION OF ACTIVATED CARBON FIBERS AND THEIR XENON ADSORPTION PROPERTIES (I)-PREPARATION AND PORE STRUCTURE CHARACTERIZATION

1. INTRODUCTION Xenon isotopics are products of nuclear fission. The nuclear plant operation may release radioactive xenon to environment, thus result in serious damage to the environment and human health. Therefore, the adsorption and concentrating of x…     

表面沸腾中接触角对液体过热度的影响

表面沸腾中接触角对液体过热度的影响刘朝，曾丹苓（重庆大学热力工程系重庆６３００４４）关键词液体过热度；接触角；涨落；统计系综１引言液体极限过热度的研究是研究沸腾热物理过程的基础。更为重要的是，液体的过热现象直接涉及到许多工程问题和技术安全问题。在实际...     

Two furano-sesquiterpenes from the South China Sea Sponge Dysidea fragilis

A new sesquiterpene, ent-furodysin (1), has been isolated from the South China Sea Sponge Dysidea fragilis, along with a known sesqui-terpene, ent-furodysinin (2). The structure and relative stereochemistry of 1 and 2 were established by spectral analysis.     

Flight dynamics over irregular asteroids

小行星探测是当前深空探测的主要方向之一,具有重要的科学意义.绝大多数小行星引力场极不规则,探测器在小行星附近运动形态复杂多样.由于同时受到中心引力、快速自旋的不规则形状摄动力、以及光压摄动等作用,探测器容易与小行星发生碰撞或逃逸.概述小行星研究现状和不规则引力场建模方法.重点介绍不规则引力场内动力学特性,包括引力平衡点、局部流形、自然周期轨道和悬停探测轨道等,尝试提出新的研究方向.     

Ni掺杂ZnS的第一性原理计算

采用基于密度泛函理论(DFT)赝势平面波方法计算了ZnS体系Ni掺杂前后的能带结构、态密度和光吸收系数曲线。结果表明:纯ZnS的能带结构是直接带隙,态密度显示属离子性较强而共价键较弱的混合键半导体材料。掺Ni的ZnS禁带宽度随掺杂量增加逐渐减小,能带简并度增大,且向低能方向移动;在价带顶出现杂质能级,说明是p型掺杂。纯ZnS在3.9 eV以下无吸收,红外透过率较高。掺Ni后吸收边红移,且在低能端(绿光区)出现新的吸收峰。     

合作博弈视角下城市道路交通拥堵收费研究

城市道路交通设施作为准公用物品,其外部效应必然导致交通拥堵的发生,实施拥堵收费的目的则是使交通拥堵产生的外部成本内部化,确保城市道路资源得到高效配置,应用经济杠杆来调节交通需求,以缓解交通拥堵.本文应用合作博弈相关理论对城市道路拥堵网络问题进行了分析,从同一时刻各个路段的通勤者数目这一角度定义拥堵成本,重点证明了拥堵成本为凸函数的城市道路拥堵网络博弈存在非空的核,拥堵成本为凹函数的城市道路交通网络博弈虽不存在非空的核,但总是存在最优的树网络,最后,结合上述结论对城市道路拥堵收费进行讨论,从理论上对拥堵收费的合理性进行了说明,并提出了进一步研究的方向.     

偶氮苯基型离子液体溶液对空气中湿度的变色响应

Room temperature ionic liquids (ILs) that can exhibit a colorimetric response to moisture in the air are rarely reported in the literature. In this study, an azophenolic IL solution exhibited a spontaneous a colorimetric response, driven by the formation of hydrogen bonding between the [PhN＝NPhO] anion and moisture in the air. This phenomenon was clearly understood using ultraviolet-visible (UV-Vis) absorption spectroscopy, nuclear magnetic resonance (NMR) spectra, experimental data, and theoretical calculations. Specifically, in the UV-Vis absorption spectra, absorption around 455 nm decreased, while the band around 343 nm increased in the IL CHCl₃ solution as time progressed; this was accompanied by a color change from orange to faint yellow. This spontaneous, self-responsive process was further observed using ¹H NMR data. When the IL solution was placed with sufficient time, all the ¹H NMR peaks of the azophenolic anion shifted downfield, but no new signals appeared in the upfield region. The reason for this was easily identified as the stimuli in the air, such as CO₂ and moisture. When pure CO₂ was bubbled through the IL CHCl₃ solution, the solution color changed from its original orange to light orange, but could not change further to faint yellow, which ruled out CO₂ gas as a stimulus. When a small amount of water was gradually added to the IL solution (MeCN solvent), the absorption band around 474 nm decreased, coupled with an increase in the absorption band around 347 nm. This was accompanied by a color change from orange to faint yellow, which was almost identical to the self-responsive process in CHCl₃ and CCl₄. Moreover, two cuvettes of IL CHCl₃ solution were placed under relative humidities of 28% and 100%, respectively; the IL CHCl₃ solution required a much longer time to exhibit a complete color change from orange to faint yellow under a lower relative humidity, demonstrating that moisture is the most likely stimulus triggering the self-responsive color change of the IL solution. As revealed by the Gaussian 09 program at the B3LYP/6-31++G(p, d) level, the distance between the oxygen atom on the azophenolic anion and the hydrogen atom on the H₂O molecule was 0.174 nm, and the corresponding angle was 171.12°. Furthermore, the atomic dipole moment corrected Hirshfeld (ADCH) charge of the oxygen atom on the azophenolic anion was −0.52, and it increased to −0.62 after the azophenolic anion interacted with the H₂O. Reduced density gradient analysis revealed that the spike corresponding to O∙∙∙H―O for the IL-H₂O complex was located at around −0.04 a.u.. All the above data indicate that the presence of hydrogen bonding rendered the IL solution responsive to the moisture stimulus, and this response was accompanied by a color change that was visible to the naked eye. To the best of our knowledge, this is the first demonstration of a colorimetric change in an IL solution in response to moisture. We hope this work can help us to gain insight into some seemingly abnormal phenomena that occur during the research process.