光纤倒像器的透过率

本文论述光纤倒像器中扭转光学纤维和尺寸及其特别的传光性能。用定性和定量的方法,分析影响光纤倒像器透过率的若干因素,给出透过率随径向位置和孔径角的变化关系。提出在制造、应用和测试这种光学元件时应该注意的有关问题。     

Tb掺杂氟化铅晶体的发光特征

用非真空Bridgman方法制备了掺有Tb杂质的氟化铅（PbF2:Tb)晶体,闯杂浓度从0.008at.%至0.6at.%。在室温下测量了该晶体的吸收和发射光谱,发现该晶体在X－射线和紫外线激发下均能够发出比较强的荧光。FbF2:Tb晶体的光吸收起源于Tb^3 离子的4f-4f跃迁,而其光发射则源于Tb^3 离子的电子分别从其激发态^5D3和^5D4能级路迁到基态^7Fj(J=6,5,4,3,2)。 荧光强度随掺杂浓度的提高而提高,当Tb^3 离子浓度较低时,以^5D3→^7FJ跃迁发射为主,当Tb^3 离子浓度较高时,则以^5D4→^7FJ跃迁发射为主。在同一晶体中,发光强度随中心所占晶格位置的改变而改变,反映出Tb^3 离子在PbF2晶体中的分布具有分凝系数大于1的特征。推测Tb^3 离子在PbF2晶体中占据Pb格位,同时产生间隙F^-离子缺陷来平衡电价。     

物理综合性实验研究

通过对综合性实验的定义、特点、开设范围、运行、保证措施,教学案例的论述,说明开展综合性实验,不仅提高了教学质量,提高了教学效率,优化了教学过程,而且在学生毕业分配及工作后完成教学、科研任务有着一定的实用价值。     

浅海中利用单水听器的声源被动测距

针对浅海声波导中远距离脉冲声源被动测距问题,提出了一种利用单水听器接收信号自相关函数进行warping变换的声源被动测距方法。理想水下声波导中,接收信号warping变换输出的傅里叶变换频谱中具有不变性频率特征,即与声源距离无关的各简正波截止频率;信号自相关函数中不同简正波相干成分也存在不变性频率特征;推导了未知声源距离时特征频率提取值与不变性频率特征之间的近似关系式。这些规律可推广到实际浅海声波导,并用于声源被动测距。利用声场计算模型来提供具有不变性频率特征的频谱,对2011年12月北黄海海域水声实验中单水听器接收的脉冲声数据进行了处理,验证了方法的有效性,测距结果和实际距离符合良好,平均测距误差在10%以内。     

PINNING EFFECT OF LEAD LANTHANUM TITANATE THIN FILMS DEPOSITED ON DIFFERENT SUBSTRATES

Pinning effect of lead lanthanum titanate (PLT) ferroelectric thin films with excess PbO of 20 mol% has been studied for deposition on diffe rent substrates. Silicon, sapphire and quartz were used as substrates on which P t/Ti or LaNiO₃ thin films were deposited as bottom electrodes. Electron probe analysis results showed that there was still a certain amount of excess Pb in PLT films after annealing at 550 ℃ for 1 h, and the amount of it was dependent on the substrate used. The distribution of excess Pb in the films was investig ated by Auger electron spectroscopy depth profile. It was shown that the substrates and the bottom electrodes had significant effects on the content and distrib ution of excess Pb in PLT films. The excess Pb and its accumulation at the inter face between the film and bottom electrode may act as pinning centers and have a pinning effect on domains, which can be observed by abnormal P-E hysteresis loops and abnormal C-V curves. The excess Pb content in the films and the accumulation of Pb at the interface were high in PLT films deposited on Pt/Ti/S i, and considerable pinning effect was observed. As LaNiO₃ would absorb most part of the excess Pb in PLT films, the content of excess Pb in the films deposited on LaNiO₃/Si was very low and the pinning effect was hardly observed.     

On Possible Sources of Heavy Neutral Particles in Cosmic Rays

We explore some possible mechanisms by which the heavy neutral cosmic particles are accelerated to gain sufficiently high kinetic energies and cause observable effects at detectors on the earth. Our results indicate that all the known sources which are based on the established theories and observations fail to give rise to very high energy with sizable flux intensity. If the heavy neutral particles of kinetic energies of GeV order indeed exist in cosmic rays, there must be certain mechanisms beyond our present knowledge of dark matter and universe evolution.     

Discrete Green's Function for Lattice Random Walk

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在岛津ICPQ-1000光谱仪上使用HG-3B型氢化物发生器

本文用岛津ＩＣＰＱ－１０００型光谱仪,并且使用了ＨＧ－３Ｂ氢化物发生器,这种发生器利用ＩＣＰ载气的压力产生的负压,自动吸入试样和ＮａＢＨ４溶液并发生氢化反应,生成的气态氢化物进入ＩＣＰ火炬并被激发。使用这种氢化物发生器同时测定了Ａｓ,Ｓｂ,Ｓｅ,Ｂｉ等４种元素,其检出限与常规气动喷雾器在比较至少降低了一个数量级。     

SIZE AND SHAPE DEPENDENCE OF THE LOWEST CONDUCTION BAND STATES IN GaAs QUANTUM DOTS

Using a recently developed new scheme, we investigated the electronic structure of the lowest conduction band states of cuboid GaAs quantum dots with different shapes and sizes in a wide range from 4 to 120a (a is the lattice constant). The critical edge length of the direct/indirect crossover in GaAs cuboid quantum dots depends on the size and shape of the quantum dots. As a deduction we also discussed the critical size of dlrect/indirect transition in GaAs quantum wires and thin films.