时间关联单光子计数中的多光子污染

从推导光子时间概率密度分布函数出发,研究了时间关联单光子计数法测量荧光寿命中,多光子修正函数的特征及其对测量误差的影响,并给出了定理关系式。     

Determination of Lifetime of Ce3+ Luminescence by Time-Correlated Single Photon Counting Method during Sonoluminescence from Aqueous CeCl3 Solution

Optics and Spectroscopy - Using a counter for single photon correlations, the flashes of sonoluminescence and sonophotoluminescence of a 0.1 M aqueous solution of CeCl3 are separated by time. The...     

The Application of Photon Counting as a Detection System in Atomic Fluorescence and Emission Spectrometry

Despite the profusion of literature associated with analytical atomic spectrometric techniques, very little has been reported concerning the development of detector systems. This is particularly surprising in view of the current trend in atomic spectrometry towards the use of non-flame atom reservoirs. These devices frequently produce weak transient signals and dc level detector systems designed for steady state measurements are in consequence often unsatisfactory. High speed recorders may be used with success providing the total response time of the various electronic components is comparable with or preferably less than that of the signal duration and only in such instances will precise measurement of the signal be achieved (1,2). The use of absolute integration techniques are obvious for this type of measurement, although their application has not been particularly forthcoming to date. Photon counting would seem to have many advantages for such purposes, although with the exception of the more general studies of Morton (3) and Malmstadt and co-workers (4) it has received so far little consideration. Indeed its use as a detection system in analytical atomic fluorescence and emission spectrometry has yet to be reported.     

乙二醇溶液中直管圆锥泡声致发光光脉冲和光谱

在U型管声致发光装置的基础上建立了一套新型的声致发光装置—直管圆锥泡声致发光装置,详细地介绍了此装置的结构和实验操作步骤,利用此装置得到了超强的发光脉冲。测量得到了乙二醇溶液中圆锥泡声致发光的发光脉冲,结果显示脉冲半宽度大约为80 μs左右,远远高于其他声致发光形式所产生的脉冲宽度,这主要是由于圆锥泡可以获得远远高于超声声致发光中气泡所能得到的能量。发光光谱为一从紫外光至可见光波长范围的连续谱,上面叠加C₂有d3Π_g→d3Π_u的跃迁形成的五个序列谱带,分别对应于Δν＝-2,Δν＝-1,Δν＝0,Δν＝1和Δν＝2;同时叠加有CN的B2Σ+→X 2Σ+跃迁形成的3个序列谱带和CH的A2Δ→X 2Π 跃迁谱带。特别是实验中测量得到了斯旺带光谱序列谱带清晰的振动结构。最后,通过与理论模拟得到的斯旺带光谱相对强度的比较,估算得到了C₂分子的振动温度大约为(4 200±200) K。     

OH自由基共振荧光的门控光子计数测量

针对气体扩张激光诱导荧光测量低浓度OH自由基系统中短寿命低强度荧光的检测需求,提出了一种共振荧光的门控光子计数测量方法,通过光电倍增管的快速门控电路设计,实现纳秒级时序内荧光的选择性测量.使用一个13级高增益端窗光电倍增管进行荧光探测,通过改变光电倍增管打拿极上的加载电压来实现光电倍增管的快速门控.电路可获得稳定的调制电压,开关延迟时间为168ns,上升沿时间约20ns.对门控电路进行器件优化及匹配参量后,采用调制打拿极d1d3d5的方式,开关引起的光电倍增管噪声降至210ns以内,调制开关比优于10~5.将门控系统应用于气体扩张激光诱导荧光系统OH自由基的荧光探测,有效获得自由基荧光信号.对307.8~308.2nm波段内的OH自由基激发谱线进行了测量,实验结果表明,门控电路能有效抑制激光杂散光的影响,实现低浓度OH自由基共振荧光信号测量.     

An Entropy-Based Anti-Noise Method for Reducing Ranging Error in Photon Counting Lidar

Photon counting lidar for long-range detection faces the problem of declining ranging performance caused by background noise. Current anti-noise methods are not robust enough in the case of weak signal and strong background noise, resulting in poor ranging error. In this work, based on the characteristics of the uncertainty of echo signal and noise in photon counting lidar, an entropy-based anti-noise method is proposed to reduce the ranging error under high background noise. Firstly, the photon counting entropy, which is considered as the feature to distinguish signal from noise, is defined to quantify the uncertainty of fluctuation among photon events responding to the Geiger mode avalanche photodiode. Then, the photon counting entropy is combined with a windowing operation to enhance the difference between signal and noise, so as to mitigate the effect of background noise and estimate the time of flight of the laser pulses. Simulation and experimental analysis show that the proposed method improves the anti-noise performance well, and experimental results demonstrate that the proposed method effectively mitigates the effect of background noise to reduce ranging error despite high background noise.     

Ion Photon Emission Microscope for Single Event Effect Testing in CIAE

Ion photon emission microscopy(IPEM) is a new ion-induced emission microscopy. It employs a broad ion beam with high energy and low fluence rate impinging on a sample. The position of a single ion is detected by an optical system with objective lens, prism, microscope tube and charge coupled device(CCD). A thin ZnS lilm doped with Ag ions is used as a luminescent material. Generation efficiency and transmission efficiency of photons in the ZnS(Ag) film created by irradiated Cl ions are calculated. A single Cl ion optical microscopic image is observed by high quantum efficiency CCD. The resolution of a single Cl ion given in this IPEM system is 6μm. Several factors influencing the resolution are discussed. A silicon diode is used to collect the electrical signals caused by the incident ions. Effective and accidental coincidence of optical images and electronic signals are illustrated. A two-dimensional map of single event effect is drawn out according to the data of effective coincidence.     

Ge薄膜特性及其在光子计数成像系统中的应用

利用电子束真空蒸镀方法制作了Ge薄膜,用作感应读出方式光子计数成像系统的电荷感应层,研究了石英玻璃衬底和陶瓷衬底上Ge薄膜的结构特征、表面形态以及各种工艺参数对薄膜电阻的影响.X射线衍射(XRD)测试表明,两种衬底上沉积的Ge薄膜均为立方相非晶态.场发射扫描电子显微镜(FESEM)图像表明石英玻璃衬底上的薄膜致密平整,陶瓷衬底上的薄膜比较粗糙,厚度较薄时,陶瓷晶界处薄膜不连续导致电阻较大.通过改变沉积速率、薄膜厚度及采用退火的方法可以控制薄膜电阻.对比了采用不同阻值电荷感应层时系统的性能,发现阻值对探测器的分辨率影响小,对计数率影响较大.     

Contribution From the Breakup-Fusion Mechanism to the Contin uum Spectra (Part I of Continuum Spectra Research)

Contribution from the breakup-fusion mechanism to continuum spectra of nuclear reaction is introduced.In this mechanism a two-step process is considered in which the projectile breaks up to two pieces in the field of target,and fusion of one piece with the target is followed.A method of finite range calculation is presented.The comparison of theoretical calculation with experimental data is shown for reactions on light and heavy targets bombarded by α-projectile.The results show that the breakup-fusion mechanism mainly contributes to continuum spectra.     

硅雪崩二极管光子辐射特性的实验研究

利用计数统计测量的方法，对工作在击穿状态下的硅雪崩光电二极管(APD)光子辐射的暂态特性以及计数统计特性进行了实验研究.将APD辐射光子的计数统计曲线与相应Poisson、热光场进行比较，发现其在采样时间为10 ms的情况下计数统计服从Super-Poisson分布.另外实验给出了APD光子辐射的光谱特性.     

Effect of Resonant Photon Emission in Radiative Heat Transfer and Generation

The effect of resonances in the photon emission rate in the radiative heat generation and transfer and the Casimir friction at the sliding of two polar dielectric plates has been studied. The resonances have different origin in the frequency ranges of the normal and anomalous Doppler effects. In the frequency range of the normal Doppler effect, the resonances are due to resonant photon tunneling between surface phonon/plas-mon polaritons of plates. Such resonances exist only at a relative sliding velocity v = 0 for two identical plates. However, the resonances may occur at v ≠ 0 for different plates. In the frequency range of the anomalous Doppler effect, the resonances are due to the excitation generation in both plates. While the resonances are finite in the frequency range of the normal Doppler effect, singular resonances are possible even in the presence of dissipation in the system in the frequency range of the anomalous Doppler effect. The resonances for identical and different sliding plates have been considered.

     

轴对称介质中光子的运动及其受激发射

采用光学度规模型，研究了光子在轴以称介质中的运动轨道，分析了光子在不稳定轨道附近的行为，进而讨论了经在激活介质中的受激发射。     

多波段相关光子光谱分布与时间相关性测量实验研究

基于相关光子的定标技术能够实现“无标准传递”绝对定标,研究相关光子的光谱辐射特性及时间相关特性对遥感器在宽波段的辐射定标具有重要意义。为满足光电探测器在宽谱段量子效率定标需求,基于相关光子的定标技术有必要从单一波段向更多波段扩展。根据自发参量下转换所满足的相位匹配条件,推导出相关光子在晶体内的非共线角计算公式,通过数值模拟相关光子光谱辐射角度分布规律,优化晶体相位匹配角,使得自发参量下转换产生的相关光子具有宽光谱分布,并且相关光子辐射角度与光谱波长能够一一对应。根据光谱分布数值模拟结果,建立了多波段相关光子的光谱分布和时间相关性测量实验系统,利用该系统测量了四对相关光子的光谱分布、符合计数、相关时间以及偏振特性。其中,测量的光谱分布范围为633~808 nm,最大光谱分布测量偏差为1.51 mm,光谱分布实验测量结果与数值模拟结果符合一致;测量了四对相关光子对的相关时间,最小相关时间为0.32 ns,并在实验中观察到了“符合三峰”现象;相关光子单光子计数及符合计数与泵浦光的偏振方向呈正弦函数关系。实验研究表明,相关光子对具有可见光~近红外宽波段分布、时间相关及偏振特性。论文研究结果在国内外尚属首次报道,该研究结果有望应用于光电探测器在多波段的辐射定标。     

光子计数式光电倍增管四象限型和弱光像增强CCD跟踪系统的性能比较

基于光子计数式光电倍增管四象限跟踪系统和弱光像增强CCD跟踪系统的基本原理，分析了这两种跟踪系统的测量噪声误差、系统控制特性和系统闭环噪声等，并重点根据实验结果分析和比较了这两种跟踪系统的性能。结果表明，光子计数式光电倍增管四象限跟踪系统的性能优于弱光像增强CCD跟踪系统。     

Continuum Micro-mechanics of Estimating Interfacial Shear Strength in Short Fiber Composites

A new continuum approach to micro-mechanics of short fiber composites yielded two separate methods of estimating the apparent interfacial shear strength and fiber orientation efficiency. The methods exploit the compilation of the effects of fiber length distribution and interfacial shear strength on strengthening efficiency into a function of strain. The In-Built Method derives a unique combination of apparent interfacial shear strength and fiber orientation efficiency being able to reproduce the experimental stress–strain curve of a short fiber reinforced composite with a very low residual standard deviation. The Boundary Method accomplishes rapid interfacial shear strength screening in materials selection by constructing and utilizing the proposed selection chart.     

Emission Spectra of BeO in Near Ultraviolet Region

Abstract

The emission spectra of isotopic BeO molecules as excited in low-pressure arc have been photographed in the region 300–350 nm at medium dispersion. The bands have been assigned to the c³II ? a³II system. The vibrational numbering was obtained from a study of the vibrational isotope effect. Vibrational constants for involved states are derived from least-squares fits of the measured bandhead wavenumbers.     

A Relation between the Spectral Profile and the Infrared Continuum of Spectra of Medium-Temperature Carbons

It is frequently found that when various organic materials are pyrolyzed at temperatures in excess of about 550°C, the infrared spectra of the chars assume a similar, almost identical profile. That would indicate that the chars had become almost or completely spectroscopically and chemically indistinguishable and unrelatable to their precursors. This topic and the possible mechanisms involved are described in detail elsewhere [1].     

Cosh-Hilbert变换反演的矩方法及其在单光子发射计算机断层成像中的应用

基于反演Hilbert变换的Tricomi公式和双曲余弦函数Taylor展开,给出一种反演双曲余弦Hilbert变换(CHT)的数值算法,并应用于单光子发射计算机断层成像.利用Taylor展开将函数的CHT变换表示为其Hilbert变换和由各阶矩组成的修正项.利用Tricomi公式得到一个关于函数各阶矩的线性方程组.通过对方程组的截断,可以求得函数的有限阶矩,并得到函数的近似重建.通过数值实验与精确重建公式进行比较,验证了算法的有效性.     

基于距离度量的LAMOST光谱中连续谱异常的自动检测

连续谱异常是指恒星光谱在获得和处理过程中由于星际消光和流量定标等原因造成连续谱严重偏离甚至中断的现象,这对光谱的谱线提取以及其他一些后续处理工作带来负面影响。提出了一种基于距离度量的连续谱异常光谱的自动检测方法,相比传统人眼检查在保证正确率的情况下大大地提高了工作效率。该方法首先通过光谱的lick线指数来确定待测光谱的恒星类型,同时对待测光谱进行归一化处理;然后分别提取待测光谱和对应类型模板光谱的连续谱;最后进行连续谱模板匹配,在每个波长点计算待测光谱和其模板光谱的流量差值,分析流量差值的分布,检验有多少差值点分布在在均值(β)附近的±α个标准差(δ)的范围内,进而可确定是否有连续谱异常。实验表明提出方法的可以快速有效的识别出连续谱异常的恒星光谱。