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为获取超快光脉冲信号,提出了一种基于光电子脉冲准线性展宽的高时间分辨二维成像技术。利用高频时变电场的线性工作区加速光电子脉冲信号,通过优化阴极激励源的电参数,选择光电子进入加速区的时刻实现光电子脉冲的准线性展宽。利用曝光时间100ps的门控选通微通道板在脉冲展宽模块的记录面进行选通曝光成像,实现高时间分辨的二维成像。为改善系统的空间分辨和成像畸变,添加轴向聚焦磁场解决电子漂移区中由电子空间电荷效应引起的时间和空间弥散,对于能量4 keV、出射角0.1°的电子束,聚焦磁场的最佳强度为0.057 T,此时阴极中心位置的空间分辨可达5 1p/mm,阴极边缘位置空间分辨稍差。基于光电子脉冲准线性展宽技术,可将漂移距离50 cm,初始脉宽10 ps的电子脉冲展宽10倍,从而可将门控MCP探测器的时间分辨提高1个量级(即10 ps以内)。 相似文献
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采用光偏转法研究气体中准分子激光与石墨和铜相互作用产生等离子体羽的特性。用空间和时间分辨的光偏转信号分析了等离子体羽的漂移速度和膨胀速度,并从光偏转信号中测得了物质波前面的激波速度。 相似文献
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基于单个矢量水听器和子空间旋转的宽容宽带双目标分辨与跟踪方法 总被引:1,自引:0,他引:1
理论证明线性信号处理可以分辨两个不完全相关的目标。针对宽带双目标问题,根据矢量水听器信号模型,设计了并行的两路结构相同的处理通道,每个通道先将接收信号做子空间旋转,分离出单个目标,然后用空间匹配滤波方法估计该目标方位。仿真研究表明,该方法适用于任意频谱结构的信号,对目标强度差和初值误差的宽容性好,可以全方位跟踪目标而性能不受目标具体方位影响,并具有时间带宽增益,在相关目标或者低信噪比情况下的性能优于宽带聚焦子空间方法。海试数据验证了该方法的可行性。该方法是一种比较实用的水下双目标分辨与跟踪方法。 相似文献
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设计并搭建了一种新的线成像激光干涉测速系统,用于小样品材料的冲击波诊断或飞片速度测量。系统采用梳状干涉条纹做为信号载体,利用1维光纤阵列+光电倍增管+数字示波器替代变像管扫描相机作为记录设备,记录伪推挽四路干涉信号,实现1 ns时间分辨和86 μm空间分辨。用它测量了脉冲激光驱动铝膜飞片的速度场,获得对比度较好的信号,数据处理结果揭示了飞片加速过程将近20 ns,飞片的平面度为14.8 mrad。实验证明,该线成像激光干涉测速系统具有一定实用性。 相似文献
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针对水下目标方位超分辨估计问题,提出了一种基于半正定规划(Sdp)的常规波束(CBF)方位超分辨算法(SdpCBF).Sdp-CBF算法基于常规波束形成获得多目标方位谱数据,利用阵列响应矩阵和半正定规划技术,精确估计目标数量和波达角方向.该算法的本质是利用阵列特性和信号能量信息获得超分辨方位估计,不用进行子空间分解,通过卷积反演的方式将阵列孔径的有限效应消除,在L2范数约束条件下重构空间谱.仿真表明,Sdp-CBF算法具有较强的噪声抑制能力,对非相干和相干信号均具有目标方位超分辨能力,在低信噪比环境下的方位分辨性能超过多重信号分类(MUSIC)等经典高分辨算法。对消声水池以及湖上实验数据的处理结果显示,Sdp-CBF算法在复杂环境中对相干信号及微弱信号具有较强的分辨能力。 相似文献
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本文成功搭建了一套集成了能谱分析功能的时间分辨光电子显微镜系统(TR-PEEM),能够对电子密度分布进行时间分辨和能量分辨的成像.这套4D显微镜在空间、时间、能量多维度获取电子动力学信息提供了前所未有的手段.本文使用184 fs的时间分辨、150 meV的能量分辨和优于150 nm的空间分辨对半导体进行了测量,在Si(111)表面的Pb岛上获得了微区光电子能谱和能量分辨的TR-PEEM图像.实验结果表明,这套系统是进行异质结载流子动力学观察的有力工具,有助于在亚微米/纳米空间尺度和超快时间尺度上加深对半导体性质的理解. 相似文献
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利用高时间分辨ESR波谱仪,对苯甲醛为光敏分子的各体系进行了CIDEP(化学诱导动态电子极化)研究,揭示了苯甲醛体系的CIDEP信号的产生过程,并进一步确认了其产生过程中的极化特征. 相似文献
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在285 nm紫外激光辐照下,用时间分辨电子自旋共振(TRESR)波谱仪研究了对苯醌/乙二醇(PBQ/EG)体系,得到了发射的苯半醌中性自由基PBQH.和乙二醇碳自由基R.(OH)2的CIDEP谱.在化学诱导动态电子极化(CIDEP)基本原理的基础上,建立合理的计算模型,编写相应的程序,对PBQH.和R.(OH)2的CIDEP形成机理进行了定量的解析.通过对不同延时下该体系各种自由基及不同机理成分的对比,明显看出由RPM形成的PBQH.比由TM形成的PBQH.衰减快.这种分析方法可以推广应用于其它体系的CIDEP实验谱的解析. 相似文献
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吩噻嗪-1,4萘醌-乙二醇体系光化学过程的时间分辨ESR研究 总被引:2,自引:2,他引:0
用时间分辨ESR方法研究了吩噻嗪(PTH)-1,4-萘醌(NQ)-乙二醇(RH)体系中的光化学过程.只观察到萘醌的中性半醌自由基NQH*的全发射极化的CIDEP(化学诱导动态极化)信号,并未观察到极化的萘醌负离子NQ·-*的CIDEP信号,表明RH与三重态NQ间的质子转移反应远比PTH与NQ间的电子转移反应为快.NQH·*的CIDEP信号随pH值的变化表明体系中同时有极化自由基NQH·*与NQH·2+*存在,并且其间有质子交换. 相似文献
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A. Kawai 《Applied magnetic resonance》2003,23(3-4):349-367
The radical-triplet pair mechanism for chemically induced dynamic electron polarization (CIDEP) created in the quenching of excited state molecules by free radicals is explained on the basis of recent time-resolved electron spin resonance spectroscopic results and theoretical studies. The CIDEP of 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) and galvinoxyl radicals exhibit various CIDEP patterns of net and mutliplet types and CIDEP phases of absorption and emission. The CIDEP patterns are described by the quartet-doublet state mixings within the radical-triplet encounter pairs. The mixings by the spin-dipolar and the hyperfine interactions are responsible for the net and the multiplet patterns, respectively. The factors controlling the CIDEP phases are the spin multiplicity of the excited state quenched by radicals and the sign of the intermolecular exchange interaction of the radical-triplet encounter pairs. In particular, the intermolecular charge transfer effect on the exchange interaction is discussed much in detail from the viewpoints of CIDEP magnitudes and phases. A CIDEP creation in the O2(1Δg)-TEMPO system is also introduced and is described by the radical-triplet pair mechanisms. Applications of this CIDEP used as a probe of O2(1Δg) in condensed phase are mentioned. 相似文献
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Akio Kawai Shuichi Mori Kazuhide Tsuji Kazuhiko Shibuya 《Applied magnetic resonance》2010,38(2):205-216
Quenching of the triplet excited state of molecular tryptophan by nitroxide radical in 1,4-dioxane and water solutions was
investigated by means of time-resolved electron paramagnetic resonance (EPR) and Fourier-transform (FT)-EPR. The chemically
induced dynamic electron polarization (CIDEP) signals with net emissive phase were recorded at these quenching events and
were analyzed through radical-triplet pair mechanism. The CIDEP time profiles were well reproduced by Bloch and kinetic equations,
assuming radical-triplet pair mechanism with the appropriate quenching rate constants. From a comparison of the simulation
and the experiment, CIDEP enhancement factor in 1,4-dioxane was determined to be −30 × P
eq, where P
eq is the spin polarization of nitroxide at thermal equilibrium. Net emissive CIDEP was also observed by FT-EPR measurements
on the nitroxide quenching of the triplet excited state of tryptophan residue in α-lactalbumin. Magnitude of CIDEP created
in α-lactalbumin/nitroxide system depends on the pH condition of α-lactalbumin solution, which is related to protein folding
dynamics. We argue the CIDEP mechanism at the α-lactalbumin surface and propose a possibility of a novel CIDEP method to probe
a protein surface and structural changes. 相似文献
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光解杜醌/氢给体均相体系的CIDEP研究 总被引:2,自引:2,他引:0
以杜醌为光敏剂,用高时间分辨电子自旋共振 (TRESR)波谱仪研究了杜醌/乙二醇体系、杜醌/氮氧自由基/乙二醇体系的化学诱导动态电子自旋极化(CIDEP).实验表明,紫外激光照射下,在杜醌/乙二醇溶液中得到以三重态机理极化为主的中性杜半醌自由基DQH*和以碳为中心的乙二醇碳自由基R*(OH)2的极化信号,而加入氮氧自由基 TEMPO后,则只观测到极化的TEMPO的E+E/A极化谱,其产生机理属于以四重态为先驱的自由基-三重态对极化机理(QP-RTPM),结合极化强度的理论计算对该体系的极化形成过程进行了分析. 相似文献
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杜醌自由基光化学路径的CIDEP研究 总被引:1,自引:0,他引:1
用自制的高时间分辨电子自旋共振波谱仪,测量得到了酸性、碱性和胶束环境下的光解杜醌/乙二醇(DQ/EG)溶液瞬态自由基的化学诱导动态电子自旋极化(CIDEP)谱.在光解均相DQ/EG溶液时,观察到了以增强发射的的中性杜半醌自由基(DQH.)的CIDEP信号;在碱性环境下(pH=9)和TX-100胶束环境下光解DQ/EG体系时得到杜醌负离子自由基(DQ-.)的CIDEP信号;在酸性环境下(pH=2.5)光解DQ/EG体系时,出现的又是中性杜半醌自由基(DQH.)的CIDEP信号.实验结果显示,DQH.由3DQ*与EG之间的氢原子转移反应生成,DQ.-由DQH.的去质子化反应生成,反应中伴随着极化转移. 相似文献
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A method for analysing EPR-time profiles of transient radicals in solution with unresolved hyperfine structure is proposed. It is based on considering the magnetic field integral of the magnetization, i.e., the total EPR signal intensity, instead of single components of overlapping EPR transitions. For a radical system involving chemical kinetics, chemically induced electron polarization (CIDEP), and spin relaxation, an analytical solution is found for the evolution of the integral magnetization in the Laplace domain. The solution in the time domain is given for the case of negligible saturation, i.e., omega2(1)T1T2 < 1. The formulae presented are suitable to avoid equivocal multi-parameter fits when analysing the results of time-resolved continuous-wave EPR experiments for the observables, which characterize the chemical kinetics, CIDEP, and electron spin relaxation of radical systems. 相似文献
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Net absorptive CIDEP generation has been demonstrated on singlet molecular oxygen and 4-oxo-2,2,6,6-tetramethyl-1-piperidinyloxyl (OTEMPO) radical system in benzene. CIDEP generation was reasonably explained in terms of the radical-triplet pair mechanism of triplet molecular oxygen-OTEMPO pair with doublet precursor. Several excited molecule-OTEMPO systems have been investigated if this CIDEP generation contributes to their CIDEP spectra. Surprisingly strong CIDEP was produced even in the presence of trace amount of dissolved oxygen, which suggests the importance of complete degassing for CIDEP studies in general systems. 相似文献
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吩噻嗪-对苯醌体系光化学过程的时间分辨ESR研究 总被引:2,自引:2,他引:0
报道了用时间分辨电子自旋共振波谱仪对吩噻嗪与对苯醌的乙二醇溶液体系的紫外光照过程进行实时检测,从测得的电子自旋共振极化港可知,电子转移和质子转移在光照过程中同时存在并且相互竞争. 相似文献