Analysis of positron annihilation lifetime data by numerical Laplace inversion: Corrections for source terms and zero-time shift errors
Analysis of positron annihilation lifetime data by numerical Laplace inversion: Corrections for source terms and zero-time shift errors
复制标题
通过数值拉普拉斯反演分析正电子湮没寿命数据：源项和零时移误差的校正
DOI：
10.1016/0168-9002(91)90367-y
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发表时间：
1991
影响因子：
1.4
通讯作者：
R. Gregory
中科院分区：
文献类型：
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作者：
R. Gregory
我们最近描述了CONTIN [S.W.]项目的修改Provencher,第一版。理论物理。在正电子湮灭寿命数据分析中出现的带有卷积核的Fredholm积分方程的解[R.B.]格雷戈里和朱永康，核。Instr。和冰毒。[a][1990]。本文描述了对程序的修改，以纠正样本和参考衰减曲线中的源项以及样本和参考数据的零时间通道位置的移位。不需要的源分量，表示为指数的离散和，可以通过修改样本数据从样本和参考数据中去除，而不需要直接了解仪器的分辨率功能。在零时间通道的位置位移高达一半的多通道分析仪的通道宽度可以被纠正。计算机模拟试验数据的分析表明，采用寿命短的参比物质可以提高湮灭率概率密度函数的质量，并表明通过淬火正电子生成自由正电子的参比物质（即强氧化剂）的寿命太长（400-450 ps），无法用上述方法对寿命短的组分提供可靠的寿命参数估计在这里。寿命小于200秒的金属，如钼（123秒）和铝（166秒），经过良好退火的单晶不会在寿命参数的估计中引入重大误差，因此首选作为参考材料。通过在聚四氟乙烯正电子湮灭中的应用，说明了我们改进的CONTIN的性能。
We have recently described modifications to the program CONTIN [S.W. Provencher, Comput. Phys. Commun. 27 (1982) 229] for the solution of Fredholm integral equations with convoluted kernels of the type that occur in the analysis of positron annihilation lifetime data [R.B. Gregory and Yongkang Zhu, Nucl. Instr. and Meth. A290 (1990) 172]. In this article, modifications to the program to correct for source terms in the sample and reference decay curves and for shifts in the position of the zero-time channel of the sample and reference data are described. Unwanted source components, expressed as a discrete sum of exponentials, may be removed from both the sample and reference data by modification of the sample data alone, without the need for direct knowledge of the instrument resolution function. Shifts in the position of the zero-time channel of up to half the channel width of the multichannel analyzer can be corrected. Analyses of computer-simulated test data indicate that the quality of the reconstructed annihilation rate probability density functions is improved by employing a reference material with a short lifetime and indicate that reference materials which generate free positrons by quenching positronium formation (i.e. strong oxidizing agents) have lifetimes that are too long (400–450 ps) to provide reliable estimates of the lifetime parameters for the shortlived components with the methods described here. Well-annealed single crystals of metals with lifetimes less than 200 ps, such as molybdenum (123 ps) and aluminum (166 ps) do not introduce significant errors in estimates of the lifetime parameters and are to be preferred as reference materials. The performance of our modified version of CONTIN is illustrated by application to positron annihilation in polytetrafluoroethylene.