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J Synchrotron Radiat. 2019 May 1;26(Pt 3):819-824. doi: 10.1107/S1600577519003503. Epub 2019 Apr 12.

Time-resolved X-ray reflection phases of the nearly forbidden Si(222) reflection under laser excitation.

Author information

1
National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan.
2
Department of Physics, National Tsing Hua University, Hsinchu 300, Taiwan.
3
Center for Measurement Standards, Industrial Technology Research Institute, Hsinchu 300, Taiwan.

Abstract

The covalent electron density, which makes Si(222) measurable, is subject to laser excitation. The three-wave Si(222)/(13 {\overline 1}) diffraction at 7.82 keV is used for phase measurements. It is found that laser excitation causes a relative phase change of around 4° in Si(222) in the first 100 ps of excitation and this is gradually recovered over several nanoseconds. This phase change is due to laser excitation of covalent electrons around the silicon atoms in the unit cell and makes the electron density deviate further from the centrosymmetric distribution.

KEYWORDS:

X-ray reflection phases; covalent electron density; laser excitation; pump–probe experiments; three-wave diffraction

PMID:
31074447
DOI:
10.1107/S1600577519003503

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