双激光脉冲打靶形成Gd等离子体的极紫外光谱辐射

高端芯片制造所需要的极紫外光刻技术位于我国当前面临35项"卡脖子"关键核心技术之首.高转换效率的极紫外光源是极紫外光刻系统的重要组成部分.本文通过采用双激光脉冲打靶技术实现较强的6.7 nm极紫外光输出.首先,理论计算Gd¹⁸⁺—Gd²⁷⁺离子最外层4d壳层的4p-4d和4d-4f能级之间跃迁、以及Gd¹⁴⁺—Gd¹⁷⁺离子最外层4f壳层的4d-4f能级之间跃迁对波长为6.7 nm附近极紫外光的贡献.其后开展实验研究,结果表明,随着双脉冲之间延时的逐渐增加,波长为6.7 nm附近的极紫外光辐射强度呈现先减弱、后增加、之后再减弱的变化趋势,在双脉冲延时为100 ns处产生的极紫外光辐射最强.并且,在延时为100 ns处产生的光谱效率最高,相比于单脉冲激光产生的光谱效率提升了33%.此外,发现双激光脉冲打靶技术可以有效地减弱等离子体的自吸收效应,获得的6.7 nm附近极紫外光谱宽度均小于单激光脉冲打靶的情形,且在脉冲延时为30 ns时刻所产生的光谱宽度最窄,约为单独主脉冲产生极紫外光谱宽度的1/3.同时...     

Cycloparaphenylene (CPP) series are molecular models for graphene armchair edges: trends in their aromaticity and cyclic conjugation are evaluated

Cycloparaphenylene ([r]CPP) and cyclacene ([r]CA) series are models for short carbon nanotubes. It is shown that armchair edges in model cycloparaphenylenes possess greater aromaticity and cyclic conjugation than do zigzag edges in model cyclacenes. According to Aihara’s bond resonance energy (BRE) and Bosanac and Gutman energy effect (ef) measurements, cycloparaphenylenes are twice as aromatic as cyclacenes. The general solution of all eigenvalues of all members of the cycloparaphenylene series is given. The origin of the recurrence of some eigenvalues are determined.     

通过超宽139La固体核磁共振波谱研究层状La(OH)2NO3

层状稀土氢氧化物是一类新型的稀土功能材料，本文采用固体核磁共振（SSNMR）方法研究了同时具备离子交换能力和非线性光学特性的层状La（OH）₂NO₃化合物，探讨了通过四极核CPMG（QCPMG）脉冲序列和变频谱图采集获取超宽¹³⁹La SSNMR谱图的方法，并描述了适用于此类实验的滤波方程和谱图重建方法.重建谱图同时包含四极核中心跃迁和卫星跃迁信息，本文使用QUEST软件对超宽¹³⁹La NMR谱图进行了模拟，获取的四极耦合常数C_Q和非对称因子η_Q均与CASTEP密度泛函理论计算值高度吻合.SSNMR实验结果证实层状La（OH）₂NO₃化合物属于非中心对称结构（P2₁），解决了对其结构长期以来存在的争论.     

三色圆偏振激光组合脉冲驱动氦原子产生椭圆偏振的阿秒脉冲

我们提出利用频率为ω,3ω和强度较弱的2ω组成的三色圆偏振激光组合脉冲驱动氦原子能够得到椭偏率较大的阿秒脉冲链的一种方法.通过强场近似方法,计算了氦原子在两色和三色圆偏振激光组合脉冲驱动下发射高次谐波谱及其合成阿秒脉冲链,比较了氦原子(初态为s态)在这两种情况下发射高次谐波谱的特点及其合成阿秒脉冲链椭偏率的大小,结果发现,在反旋的两色ω,3ω激光脉冲基础上加入了频率为2ω的第三色激光脉冲联合作用到氦原子上,所得到的阿秒脉冲链的椭偏率相对于双圆场情况下有所增加,通过调整ω,3ω激光的强度比,并且选择适当的第三色激光的强度,对初态为s态的原子,仍能够得到具有较大椭偏率的阿秒脉冲链.     

Stabilization of self‐assembled microdroplets using short chain alcohols

The condensation of water vapor on a volatile polymeric solution leads to a porous surface after evaporation of both solvent and water. However, the stabilization of the water microdroplet is of great importance, which can be achieved using specific polymer or adding a third substance to the polymer solution. Short chain alcohols (methanol, ethanol, and n‐propanol) are utilized to fabricate a self‐assembled porous honeycomb film of linear, low molecular weight polystyrene using the breath figure technique. A combination of breath figure processing and the effect of alcohol on a water droplet can stabilize the pattern and make pores on the surface of the polymer film. The quality of the porous honeycomb film is strongly dependent on the type of alcohols and the concentration of polymer. In a specific range of polymer and alcohol concentration, pores cover all the surface of the polymer film. This method offers the possibility of producing a honeycomb structure with no trace of additive residual after the fabrication process and avoiding polymer modification. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 709–718     

基于耦合Ginzburg-Landau方程的石墨烯锁模光纤激光器的暗暗孤子解及其稳定性

以耦合Ginzburg-Landau方程为模型,对石墨烯锁模光纤激光器中脉冲的动力学行为进行了详细地研究.首先,采用拟解法推导了该方程组的啁啾类暗暗孤子对解;其次,对啁啾类暗暗孤子对的传输特性及稳定性进行了数值研究.结果表明:合理选择系统参数,不仅可以得到啁啾类暗暗孤子对的精确解,而且该精确解还可以在一定的扰动下稳定传输.相关结果将为设计和改善石墨烯锁模光纤激光器的性能提供一定的理论依据.     

无序激光晶体及其超快激光研究进展

激光是受激辐射的光放大,所辐射的波长取决于增益介质中关键电子的能级结构,特别是其最外层电子的状态决定了可能实现的激光特性。激光发展60年来,激光晶体作为激光的重要激活材料,推动了激光技术的进步和普及,是一个研究历史长而又异常活跃的研究领域。当前,超短超强脉冲激光在加工、医疗、国防等关系国计民生的领域有重要需求,适合超短超强激光的激光晶体成为了本领域的研究热点,其关键是揭示最外层电子的影响因素及设计和生长具有宽波段发射性能的激光晶体。本论文从探讨影响激活离子光谱性能的关键因素出发,综述了以本课题组十余年研究的10余种无序激光晶体为主要部分的研究结果和进展,涉及晶体生长、晶体物理、激光器件设计及应用等工作,包含了高级、中级和低级对称性晶体及其获得的最短脉冲激光结果,希望能为本领域的后续研究提供一定的参考和借鉴。     

一种经验型疲劳小裂纹扩展模型

金属材料疲劳寿命由裂纹萌生和裂纹扩展寿命两部分组成，其中对于萌生寿命中的小裂纹分析是精确描述裂纹萌生寿命的关键．而小裂纹在扩展过程中由于尺寸相对较小，导致传统线弹性断裂力学预测方法失效，需要对其进行改进，考虑裂纹尖端塑性区引起的残余压应力对小裂纹扩展速度的影响．本文针对此问题进行了初步分析，通过对塑性区引起的残余应力的量化，结合小裂纹门槛值特性，提出了一种经验型修正的小裂纹扩展模型，用于定量预测裂纹的萌生寿命．使用铝合金6082-T6缺口试样进行了疲劳实验，并与理论结果进行了对比，验证了所提模型的有效性．     

Electrochemical Characterization and Voltammetric Determination of Benzoyl Derivatives of Phenobarbital Using Glassy Carbon Electrode

The electrochemical behavior of a number of benzoyl barbiturates was studied using a glassy carbon electrode (GCE). The kinetics of the electrode process is determined, the contribution of physical adsorption to the electrochemical process is estimated, and the mechanism of the possible electrochemical reaction is proposed. It is shown that the electrochemical reduction potentials of benzoyl phenobarbital derivatives are determined by the LUMO energies, calculated by the B3LYP 6‐311+G method. It is established that the process is quasi‐reversible, complicated by adverse reactions. The influence of halogen type and its position in the benzoyl residue of the studied substances on the analytical signal is established. The effective values of the dissociation constants of various forms of benzoyl derivatives were calculated using the example of halonal, for which the values 3.16 ? 10^?8 and 6.31 ? 10^?12, respectively, were found.     

Review on ionization and quenching mechanisms of Trichel pulse

Trichel pulse is a kind of pulsed mode in negative DC corona discharge, which has attracted significant attention because of its considerable applications in industry. Over eighty years, plenty of effort including simulations and experiments has been spent to reveal the ionization and quenching mechanisms of Trichel pulse. By revisiting and summarizing the basic characteristics and well-accepted ionization and quenching mechanisms, this review provides a basic understanding and the current status of Trichel pulse.