Polarized x-ray emission studies of methyl chloride and the chlorofluoromethanes.
Polarized x-ray emission studies of methyl chloride and the chlorofluoromethanes.
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氯甲烷和氯氟甲烷的偏振 X 射线发射研究。
DOI：
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发表时间：
1991
期刊：
影响因子：
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通讯作者：
R. Perera
中科院分区：
文献类型：
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作者：
D. Lindle;P. L. Cowan;T. Jach;R. Lavilla;R. Deslattes;R. Perera
一种新的技术敏感的分子取向和几何形状，并基于测量X射线发射的偏振，已被应用于含氯分子甲基氯（CH{sub 3}Cl）和氯氟甲烷（CF{sub 3}Cl，CF{sub 2}Cl{sub 2}，和CFCl{sub 3}）在气相中。选择性激发后，使用单色同步辐射在Cl {ital K}-边缘（Cl 1 s）近阈值区域，偏振选择性X射线发射研究揭示了高度偏振的分子{ital价}的X射线荧光的所有四个分子。偏振发射的取向度和取向度对Cl {italK}边附近的入射激发能敏感。在某些情况下，X射线发射的偏振方向会因入射激发能的微小变化（几eV）而反转。它表明，偏振X射线发射技术可以用来推断，直接从实验中，占据和未占据价分子轨道的对称性，在吸收和发射的各向异性，取向和几何信息。这表明，X射线偏振荧光现象，这里报道的简单分子，可以作为一种新的方法来研究更复杂的系统在各种环境中。
A new technique sensitive to molecular orientation and geometry, and based on measuring the polarization of x-ray emission, has been applied to the Cl-containing molecules methyl chloride (CH{sub 3}Cl) and the chlorofluoromethanes (CF{sub 3}Cl, CF{sub 2}Cl{sub 2}, and CFCl{sub 3}) in the gas phase. Upon selective excitation using monochromatic synchrotron radiation in the Cl {ital K}-edge (Cl 1s) near-threshold region, polarization-selective x-ray emission studies reveal highly polarized molecular {ital valence} x-ray fluorescence for all four molecules. The degree {ital and} the orientation of the polarized emission are observed to be sensitive to the incident excitation energy near the Cl {ital K} edge. In some cases, the polarization direction for x-ray emission reverses for small changes in incident excitation energy (a few eV). It is shown that the polarized x-ray emission technique can be used to infer, directly from experiment, symmetries of occupied and unoccupied valence molecular orbitals, an- isotropies in absorption and emission, and orientational and geometrical information. It is suggested that the x-ray polarized-fluorescence phenomenon, reported here for simple molecules, can be used as a new approach to study more complicated systems in a variety of environments.