Undistorted X-ray Absorption Spectroscopy Using s-Core-Orbital Emissions
Undistorted X-ray Absorption Spectroscopy Using s-Core-Orbital Emissions
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DOI：
10.1021/acs.jpca.6b01699
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发表时间：
2016-05-12
影响因子：
2.9
通讯作者：
Aziz, Emad F.
中科院分区：
文献类型：
--
作者：
Golnak, Ronny;Xiao, Jie;Aziz, Emad F.
X射线共振吸收的二次发射、荧光产额(FY)或电子产额(EY)的检测在X射线吸收光谱(XAS)测量中被广泛采用，当一次吸收过程不能在透射式模式下被直接探测时。然而，在弛豫过程和随后发射的粒子(电子或光子)通过样品的传输中固有的各种光谱失真效应破坏了发射信号与X射线吸收系数的比例。本文在模型体系FeCl3水溶液中，在Fe L边激发能下，对多个辐射(FY)和非辐射(EY)衰变通道进行了实验研究。对不同衰变通道的实验光谱进行了系统的比较，并与只涉及吸收过程的理论模拟的Fe L边XA谱进行了比较，结果表明，对Fe3s>；2p部分荧光产额的探测产生了真正的Fe L边XA谱。从这一特殊的衰变通道中概括出的两个关键特征--零轨道角动量(即S轨道)和核能级发射--为未来获得无失真的X射线吸收光谱设定了指导方针。
Detection of secondary emissions, fluorescence yield (FY), or electron yield (EY), originating from the relaxation processes upon X-ray resonant absorption has been widely adopted for X-ray absorption spectroscopy (XAS) measurements when the primary absorption process cannot be probed directly in transmission mode. Various spectral distortion effects inherent in the relaxation processes and in the subsequent transportation of emitted particles (electron or photon) through the sample, however, undermine the proportionality of the emission signals to the X-ray absorption coefficient. In the present study, multiple radiative (FY) and nonradiative (EY) decay channels have been experimentally investigated on a model system, FeCl3 aqueous solution, at the excitation energy of the Fe L-edge. The systematic comparisons between the experimental spectra taken from various decay channels, as well as the comparison with the theoretically simulated Fe L-edge XA spectrum that involves only the absorption process, indicate that the detection of the Fe 3s -> 2p partial fluorescence yield (PFY) gives rise to the true Fe L-edge XA spectrum. The two key characteristics generalized from this particular decay channel-zero orbital angular momentum (i.e., s orbital) and core-level emission-set a guideline for obtaining undistorted X-ray absorption spectra in the future.