Baer Tomas, Tuckett Richard P
Chemistry Department, University of North Carolina, Chapel Hill, NC 27599-3290, USA.
Chemistry Department, University of Birmingham, B15 2TT, UK.
Phys Chem Chem Phys. 2017 Apr 12;19(15):9698-9723. doi: 10.1039/c7cp00144d.
The history and evolution of molecular threshold photoelectron spectroscopy and threshold photoelectron photoion coincidence spectroscopy (TPEPICO) over the last fifty years are reviewed. Emphasis is placed on instrumentation and the extraction of dynamical information about energy selected ion dissociation, not on the detailed spectroscopy of certain molecules. Three important advances have expanded greatly the power of the technique, and permitted its implementation on modern synchrotron radiation beamlines. The use of velocity focusing of threshold electrons onto an imaging detector in the 1990s simultaneously improved the sensitivity and electron energy resolution, and also facilitated the subtraction of hot electron background in both threshold electron spectroscopy and TPEPICO studies. The development of multi-start multi-stop collection detectors for both electrons and ions in the 2000s permitted the use of the full intensity of modern synchrotron radiation thereby greatly improving the signal-to-noise ratio. Finally, recent developments involving imaging electrons in a range of energies as well as ions onto separate position-sensitive detectors has further improved the collection sensitivity so that low density samples found in a variety of studies can be investigated. As a result, photoelectron photoion coincidence spectroscopy is now well positioned to address a range of challenging problems that include the quantitative determination of compositions of isomer mixtures, and the detection and spectroscopy of free radicals produced in pyrolysis or discharge sources as well as in combustion studies.
本文综述了分子阈光电离光谱和阈光电离-光离子符合光谱（TPEPICO）在过去五十年中的历史与发展。重点在于仪器设备以及关于能量选择离子解离的动力学信息提取，而非特定分子的详细光谱。三项重要进展极大地扩展了该技术的能力，并使其能够在现代同步辐射光束线上得以应用。20世纪90年代将阈电子速度聚焦到成像探测器上，同时提高了灵敏度和电子能量分辨率，还便于在阈电子光谱和TPEPICO研究中扣除热电子背景。21世纪开发的用于电子和离子的多起始-多停止采集探测器，使得能够利用现代同步辐射的全部强度，从而极大地提高了信噪比。最后，近期涉及在一系列能量下对电子以及对离子成像到单独的位置敏感探测器上的进展，进一步提高了采集灵敏度，从而能够研究各种研究中发现的低密度样品。因此，光电子-光离子符合光谱现在已具备充分条件来解决一系列具有挑战性的问题，包括异构体混合物组成的定量测定，以及在热解或放电源以及燃烧研究中产生的自由基的检测和光谱分析。
