Integrated intensities of our model calculations and our experimental results associated with different features of the covariance maps relative to the intensity of the feature associated with the PAP process

<b>Table 2.</b> Integrated intensities of our model calculations and our experimental results associated with different features of the covariance maps relative to the intensity of the feature associated with the PAP process. The experimental values were corrected for the collection–detection efficiency of the spectrometer used, taking into account a decrease of about 50% for energetic valence and Auger electrons. <strong>Abstract</strong> We report on a detailed investigation into the electron emission processes of Ne atoms exposed to intense femtosecond x-ray pulses, provided by the Linac Coherent Light Source Free Electron Laser (FEL) at Stanford. The covariance mapping technique is applied to analyse the data, and the capability of this approach to disentangle both linear and nonlinear correlation features which may be hidden on coincidence maps of the same data set is demonstrated. Different correction techniques which enable improvements on the quality of the spectral features extracted from the covariance maps are explored. Finally, a method for deriving characteristics of the x-ray FEL pulses based on covariance mapping in combination with model simulations is presented.

表2. 相较于与光电子雪崩过程（Photoelectron Avalanche Process, PAP）相关特征的强度，本研究模型计算与实验结果中，协方差映射（covariance maps）各不同特征的积分强度。实验数值已针对所用光谱仪的收集-探测效率进行校正，同时考虑到高能价电子（energetic valence electrons）与俄歇电子（Auger electrons）的信号衰减幅度约为50%。摘要：本研究针对氖（Ne）原子受斯坦福直线加速器相干光源（Linac Coherent Light Source）产生的强飞秒X射线脉冲辐照时的电子发射过程展开详细探究，并汇报相关研究成果。本研究采用协方差映射技术对实验数据进行分析，证实该方法可有效分离同一数据集符合映射（coincidence maps）中可能被掩盖的线性与非线性关联特征。本研究还探索了多种校正技术，以提升从协方差映射中提取的光谱特征的质量。最后，本研究提出一种结合协方差映射与模型模拟的方法，用于获取X射线自由电子激光（Free Electron Laser, FEL）脉冲的相关特性。