Statistical properties of the photoelectron energy spectrum generated by an intense laser pulse and a continuous X-ray

This study shows that the photoelectron energy spectrum generated by an intense laser pulse in the presence of a continuous X-ray has interesting and useful statistical properties. The total photoionization production is linearly propor- tional to the time duration of the laser pulse and the square of the beam size. The spectral double energy-integration is an intrinsic value of the laser-assisted X-ray photoionization, which linearly depends on the laser intensity and which quantita- tively reflects the strengths of the laser-field modulation and the quantum interference between photoelectrons. The spectral energy width also linearly depends on the laser intensity. These linear relationships suggest new methods for the in-situ measurement of laser intensity and pulse duration with high precision.     

Improving the precision of fluorescence lifetime measurement using a streak camera

Streak camera has high temporal resolution and high sensitivity, and is a powerful tool in biomedical study to measure fluorescence lifetime and perform fluorescence lifetime imaging. However, nonuniformity of the gain in the streak tube and nonlinearity of the sweeping speed limit the precision of fluorescence lifetime measurement, particularly when fluorescence lifetimes are short. We have constructed a two-photon excitation fluorescence lifetime measurement system that is based on a synchroscan streak camera and have developed accordingly a method to correct the effect of gain nonuniformity and nonlinearity of sweeping speed on the measurement precision. A continuous-wave laser of high stability is used to calibrate the gain of the streak camera, and a Fabry-Perot etalon is used to calibrate the nonlinearity of the sweeping speed. Fitting algorithms are used to correct the gain of the streak camera and nonlinearity of the sweeping speed respectively, which significantly improves the measurement precision of the system, as characterized through the fluorescence lifetime of the short-lived fluorescence dye, Rose Bengal. Experimental results show that the measurement fluctuation of the lifetime has been improved from more than 10% to 2% after correcting the effects of gain nonuniformity and sweeping speed nonlinearity.     

钚同位素成分及总质量测量的可行性探讨

利用MCNP4B程序,通过一个实例探讨了钚的同位素成分及总质量测量的理论可行性.首先利用假想的γ射线源确定出不同能量γ射线穿透容器的相对效率曲线;然后将实际的钚样品放入容器,通过容器外各种特征γ射线强度的测量可以推算出钚的同位素成分;最后测量出系统总中子泄漏数,便可求得钚的总质量. One possible method of measurement of isotopic composition and mass for plutonium is discussed and its feasibility in theory is demonstrated by the MCNP4B package in this paper. The relative efficiency ratio curve for the container where the plutonium sample is put in can be computed by assigning an arbitrary γ ray source in the sample . Once the relative efficiency ratio for the container is known, the isotopic components for plutonium can be induced by assigning the real γ ray source in the sample and...     

The effects of spectrograph slit modes on the accuracy of stellar radial velocity measurement and atmospheric parameter estimation

Spectrograph slit is conventionally used to enhance the spectral resolution and manage how much light can be allowed to enter spectrograph.The narrow slit provides a higher resolution but sacrifices efficiency of spectrograph and results in a low signal to noise ratio(S/N) spectra product.We take GuoShouJing telescope as an example and carry out a series of experiments to study how its 2/3 slit mode affects the precision of stellar radial velocity measurement and atmosphere parameters estimate.By transforming the resolution and adding a Gaussian White Noise to the extremely high quality spectra from the Sloan Digital Sky Survey,we generate synthetic stellar spectra of various brightness with different S/Ns.Comparing the measurements on these noise added spectra with the original high quality ones,we summarize the influences of the 2/3 slit mode on the measurement accuracy of stellar radial velocity and atmospheric parameters.     

Super-sensitivity measurement of tiny Doppler frequency shifts based on parametric amplification and squeezed vacuum state

The precision measurement of Doppler frequency shifts is of great significance for improving the precision of speed measurement. This paper proposes a precision measurement scheme of tiny Doppler shifts by a parametric amplification process and squeezed vacuum state. This scheme takes a parametric amplification process and squeezed vacuum state into a detection system, so that the measurement precision of tiny Doppler shifts can exceed the Cram′er–Rao bound of coherent light. Simultaneously, a simulation study is carried out on the theoretical basis, and the following results are obtained: for the signal light of Gaussian mode, when the amplification factor g = 1 and the squeezed factor r = 0.5, the measurement error of Doppler frequency shifts is 14.4% of the Cramer–Rao bound of the coherent light in our system. At the same time,when the local light mode and squeezed vacuum state mode are optimized, the measurement precision of this scheme can be further improved by ■ times, where n is the mode-order of the signal light.     

Vibrational spectra and intramolecular vibrational redistribution in methane and its isotopomers

An improved U(2) algebraic model is introduced to study the stretching and bending vibrational spectra of methane and its isotopomers.The algebraic model with fewer parameters reproduces the experimental spectra with good precision.Moreover,the obtained parameters describe well the correct behavior of isotopic substitution.It is shown that the Fermi resonance leads to a very fast intramolecular vibrational redistribution among stretches and bends.     

Laser Phase Determination and Transfer Function to Directly Measure the Temporal Structure of a Narrow Bandwidth Attosecond EUV Pulse

A laser phase determination method and a transfer function that includes a proportional term of a measured photoelectron energy spectrum are presented to directly measure the detailed temporal structure of a narrow bandwidth attosecond extreme-ultraviolet （EUV） pulse. The method is based on the spectrum measurement of an electron generated by EUV photo-ionization interacting with a femtosecond laser field. The results of the study suggest that measurements should be taken at 0° or 180° with respect to the linear laser polarization. The method has a temporal measurement range of about half a laser oscillation period. The temporal resolution also depends on the jitter and control precision of the laser and EUV pulses.     

布鲁克海文的新(g-2)实验

布鲁克海文的Ｅ８２１是一个新的测量μ介子反常磁矩的高精度实验．要求达到的精度为０．３５ｐｐｍ,比ＣＥＲＮ的实验精度高２０倍．精度的提高将提供对ＴｅＶ质量范围虚粒子的敏感性及为发现标准模型以外新物理打开一个重要的窗口．同时Ｅ８２１的超高精度在技术及物理上提出了不寻常的挑战.A new measurement of the muon anomalous magnetic moment (BNL E821) aims to obtain a precision of 0.35 ppm which is 20 times higher than that of CERN measurement. This increase in precision will provied a sensitivity to virtual particles into the TeV mass range and open a substantial window for the discovery of new physics beyond the standard model. Meanwhile the ultahigh precision aimed for in the BNL experiment gives unusual challenges in physics and in technology.     

Border effect-based precise measurement of any frequency signal

Limited detection resolution leads to fuzzy areas during the measurement, and the discrimination of the border of a fuzzy area helps to use the resolution stability. In this way, measurement precision is greatly improved, hence this phenomenon is named the border effect. The resolution fuzzy area and its application should be studied to realize highresolution measurement. During the measurement of any frequency signal, the fuzzy areas of phase-coincidence detection are always discrete and irregular. In this paper the difficulty in capturing the border information of discrete fuzzy areas is overcome and extra-high resolution measurement is implemented. Measurement precision of any frequency-signal can easily reach better than 1 × 10-11/s in a wide range of frequencies, showing the great importance of the border effect. An in-depth study of this issue has great significance for frequency standard comparison, signal processing, telecommunication,and fundamental subjects.     

Quantum metrology with coherent superposition of two different coded channels

We investigate the advantage of coherent superposition of two different coded channels in quantum metrology. In a continuous variable system, we show that the Heisenberg limit 1/N can be beaten by the coherent superposition without the help of indefinite causal order. And in parameter estimation, we demonstrate that the strategy with the coherent superposition can perform better than the strategy with quantum SWITCH which can generate indefinite causal order. We analytically obtain the general form of estimation precision in terms of the quantum Fisher information and further prove that the nonlinear Hamiltonian can improve the estimation precision and make the measurement uncertainty scale as 1/Nm for m ≥ 2. Our results can help to construct a high-precision measurement equipment, which can be applied to the detection of coupling strength and the test of time dilation and the modification of the canonical commutation relation.     

应用于碳同位素丰度测量的激光频率刻度系统研究

对应用于激光吸收光谱法碳同位素丰度测量中的激光频率实时刻度系统进行研究. 采用不同自由光谱范围的共焦法布里-珀罗干涉仪对测量过程中的激光扫描频率进行实时测量. 分别采用线性内插法和多项式拟合法对激光频率每次扫描过程中的频率非线性进行分析,通过对4976–4980 cm^-1波段CO₂吸收谱的多次测量平均的实验结果与HITRAN-2008数据库相应的吸收峰数据进行比较,得到两种方法的激光频率刻度精度均可达到10^-4 cm^-1,线性内插法的刻度精度要好于多项式拟合法. 验证了激光频率实时刻度系统在碳同位素丰度测量中应用的可行性. 关键词： 激光频率实时刻度 共焦法布里-珀罗干涉仪 同位素丰度测量 激光吸收光谱法     

Pu300能量窗钚年龄算法

美国LLNL提出了采用钚材料γ谱的330—350keV(Pu300)能量窗计算钚年龄, 用此能量窗建立了相关钚年龄算法, 并对几个不同样品的谱数据进行了计算, 并将其结果与PC/FRAM的结果进行比较, 结果表明两者吻合得比较好.     

基于傅里叶变换红外光谱技术测量大气中CO_2的稳定同位素比值

长期监测大气中CO_2及其稳定同位素不仅可以获得CO_2源和汇信息,还可以确定不同排放源对大气中CO_2的贡献.傅里叶变换红外光谱技术是目前大气中痕量气体柱浓度高精度遥测的一种重要方法.本研究基于地基高分辨率傅里叶变换红外光谱仪采集的近红外太阳吸收光谱反演出大气中CO_2的稳定同位素~(13)CO_2和~(12)CO_2.在选择的~(13)CO_2的三个光谱窗口和~(12)CO_2的两个光谱窗口光谱拟合残差都很小,光谱拟合质量高.实验观测期间CO_2同位素~(13)CO_2和~(12)CO_2的反演误差平均值分别为(1.18±0.27)%和(0.89±0.25)%;利用Allan方差计算出观测系统的碳同位素比值δ~(13)C的测量精度为0.041‰.获得了2015年9月18日至2016年9月24日一年内大气中碳同位素比值δ~(13)C的长时间序列.结果表明,在整个测量期间δ~(13)C在-7.58‰--11.66‰范围内变化,平均值为(-9.5±0.57)‰;δ~(13)C有着明显的季节变化,冬季最小,夏季最大.分析了取暖导致的化石燃料燃烧排放增多是冬季大气中CO_2重同位素~(13)CO_2贫化的原因.观测结果显示了高分辨率傅里叶变换红外光谱仪具有准确和高精度观测大气中CO_2的稳定同位素和同位素比值δ~(13)C的能力.     

2 μm附近CO2谱线参数测量及应用

吸收光谱技术用于痕量气体浓度监测,特别是在气体分子稳定同位素丰度探测中,吸收谱线参数的准确性非常重要,目前普遍使用的HITRAN数据库中给出的各项参数具有一定的不确定性。为利用2.0 μm激光波段进行CO₂浓度及其同位素丰度探测,需要对该波段的CO₂吸收谱线参数进行校准,采用窄线宽分布反馈式二极管激光器作为光源,结合自行搭建的谱线参数测量系统,采集了2.0 μm波段10条CO₂吸收谱线,获得了各谱线的位置、强度、自加宽系数和N₂加宽系数,并与HITRAN2012数据库中相应的数据进行对比发现两者之间吻合较好,CO₂谱线强度和自加宽系数相对偏差均小于2%。实测实验室大气的CO₂浓度为440 ppm,13CO₂的丰度值δ为-9‰。测量结果为该波段应用于CO₂浓度及13CO₂同位素丰度的实时在线探测提供了重要参考依据。     

2.0μm附近模拟呼吸气体中~(13)CO_2/~(12)CO_2同位素丰度的高精度实时在线测量

采用可调谐二极管激光吸收光谱技术,结合一新型多通池搭建了一套模拟呼吸气体中CO_2同位素丰度的测量装置.气体的压强、温度和流速被很好地控制且均能保持长期的稳定性;采用三次多项式拟合光谱基线,对光谱进行归一化,很好地消除了功率变化对测量结果的影响;利用移窗-回归技术消除频率漂移对同位素丰度测量的影响.实验结果表明:移窗-回归法的引入不仅延长了系统的稳定时间,还提高了系统的测量精度;小波去噪的应用获得了比多光谱平均法高2倍的信噪比;系统的稳定时间为100 s;Kalman滤波后系统测量精度为0.067‰.     

New method for isotopic ratio measurements of atmospheric carbon dioxide using a 4.3 μm pulsed quantum cascade laser

We present a new approach to the measurement of stable isotopic ratios of carbon dioxide using a near-room-temperature pulsed quantum cascade laser and a spectral ratio method based upon dual multiple pass absorption cells. The spectral ratio method improves precision and accuracy by reducing sensitivity to variations in the laser tuning rate, power and line width. The laser is scanned across three spectral lines (near 2310 cm^-1) quantifying three CO₂ isotopologues: ¹²C¹⁶O₂, ¹³C¹⁶O₂ and ¹²C¹⁶O¹⁸O. Isotopic ratios are determined simultaneously with a precision of 0.2δ for each ratio with a one-second measurement. Signal averaging for 400 s improves the precision to better than 0.03δ for both isotopic ratios (¹³ R and ¹⁸ R). Long-term accuracy of 0.2 to 0.3δ is demonstrated with replicate measurements of the same sample over a one-month period. The fast time response of this instrument is suitable for eddy flux measurements. PACS 07.57.Ty; 42.62.Fi; 92.70.Cp; 91.67.Rx     

一种高准确度、高可靠的红外光电时刻测量系统

针对靶场试验对测量仪器的准确度及可靠性的特殊要求,开发了一种基于嵌入式PC/104模块和大规模可编程逻辑器件CPLD的红外光电时刻测量系统.介绍了该系统的组成、测量原理及其实现途径.靶场实验结果表明,该系统设计环境适应能力强,能可靠地工作在－35～45℃的环境下;测量准确度高,测时误差小于30 μs.     

光谱辐照度测量的数学模型及其方法研究

光谱辐照度是光谱辐射计量中最基本的参数，是研究各种辐射源及光电探测器特性的重要依据。为提高光谱辐照度的测量精度和量值溯源等问题，国防科工委光学计量一级站采用BB3200K高温黑体作为基准的辐射源，以新型辐射测温法为基础，通过一系列光辐射理论和几何原理推导出辐射温度与辐射光功率之间的关系；通过对光辐射功率的绝对测量，并结合低温辐射计，从而完成了光谱辐照度量值的精度测量。该理论奠基了以探测器为基础的新的光辐射量传体系。主要介绍了在光谱辐照度标准装置的项目中复现光谱辐照度所建立的数学模型及新的测试方法，给出了测量结果，并简要介绍了基于该理论的测量装置的组成及原理。     

基于指示克立格法的最佳激发波长和最佳发射波长的确定

激发波长和发射波长是分子荧光光谱测量的重要参数,它的选择影响分子荧光光谱的测量以及其后续研究的精确度。由于如HITACHI F-4500 荧光分光光度计等一些光谱仪器的测量精度达不到一些光谱分析技术的要求以及测量数据的有限,在实际工作中,利用已测量的光谱数据,通过插值生成所需要的光谱数据,就成为一种有效的解决方法。因此,文章使用指示克立格法对一定体积分数的乙醇溶液的最佳激发波长和最佳发射波长的确定进行了研究。基于指示克立格法求取的最佳激发波长和最佳发射波长分别是226.9和337.1 nm,经验证其值是准确的。此外,文章采用相对标准偏差对插值结果进行了评价。结果表明在分子荧光光谱测量中基于指示克立格法确定最佳激发波长和最佳发射波长是可行的,这为最佳激发波长和最佳发射波长的确定提供了一种新的方法。     

光谱滤波技术对星等测量精度的影响

 白天对空间目标进行观测时,采用光谱滤波技术可以提高光电系统的极限星等探测能力。针对光谱滤波探测特点,基于现有测量方法,结合光谱反射特性,分析了光谱滤波技术对测量精度的影响,给出了修正方法;利用光电系统对某空间目标进行了实际测量,根据事后修正方法进行了仿真研究,对实际测量值与事后修正值进行了比对分析。分析表明：光谱滤波技术虽然提高了光电系统的探测能力,但对测量精度带来了较大的影响,最大精度可为0.5等星。