Inkinen Juho, Niskanen Johannes, Talka Tuomas, Sahle Christoph J, Müller Harald, Khriachtchev Leonid, Hashemi Javad, Akbari Ali, Hakala Mikko, Huotari Simo
Department of Physics, P.O. Box 64, FI-00014 University of Helsinki, Helsinki, Finland.
ESRF - The European Synchrotron, CS 40220, F-38043 Grenoble Cedex 9, France.
Sci Rep. 2015 Nov 16;5:15851. doi: 10.1038/srep15851.
A classic example of solid-state topochemical reactions is the ultraviolet-light induced photodimerization of α-trans-cinnamic acid (CA). Here, we report the first observation of an X-ray-induced dimerization of CA and monitor it in situ using nonresonant inelastic X-ray scattering spectroscopy (NRIXS). The time-evolution of the carbon core-electron excitation spectra shows the effects of two X-ray induced reactions: dimerization on a short time-scale and disintegration on a long time-scale. We used spectrum simulations of CA and its dimerization product, α-truxillic acid (TA), to gain insight into the dimerization effects. From the time-resolved spectra, we extracted component spectra and time-dependent weights corresponding to CA and TA. The results suggest that the X-ray induced dimerization proceeds homogeneously in contrast to the dimerization induced by ultraviolet light. We also utilized the ability of NRIXS for direct tomography with chemical-bond contrast to image the spatial progress of the reactions in the sample crystal. Our work paves the way for other time-resolved studies on chemical reactions using inelastic X-ray scattering.
固态拓扑化学反应的一个经典例子是α-反式肉桂酸（CA）的紫外光诱导光二聚化反应。在此，我们报告了首次观察到的X射线诱导的CA二聚化反应，并使用非共振非弹性X射线散射光谱（NRIXS）对其进行原位监测。碳芯电子激发光谱随时间的变化显示了两个X射线诱导反应的影响：短时间尺度上的二聚化和长时间尺度上的分解。我们通过对CA及其二聚化产物α-特鲁西利酸（TA）的光谱模拟，深入了解二聚化效应。从时间分辨光谱中，我们提取了对应于CA和TA的组分光谱以及随时间变化的权重。结果表明，与紫外光诱导的二聚化不同，X射线诱导的二聚化是均匀进行的。我们还利用NRIXS具有化学键对比度的直接断层成像能力，对样品晶体中反应的空间进程进行成像。我们的工作为使用非弹性X射线散射对化学反应进行其他时间分辨研究铺平了道路。
