Time-Resolved X-ray Reflection Phases of Nearly Forbidden Si(222) Reflection Under Laser Excitation.
Y.-W. Tsai1*, Y.-Y. Chang1, Y.-H. Wu2, K.-Y. Lee2, S.-C. Weng1, J.-J. Lee1, M.-S. Chiu1, S,-L. Chang1,2
1National Synchrotron Radiation Research Center, Hsinchu, Taiwan
2Physics, National Tsing Hua University, Hsinchu, Taiwan
* Presenter:Y.-W. Tsai
The covalent electron density, which makes Si(222) measurable, is subject to laser excitation. The three-wave Si(222)/(13-1) diffraction at 7.82 keV is used for phase measurement. The phase is related with the distribution of the electron density in a unit cell. It is found that the laser excitation causes a relative phase change of -5 degrees of Si(222) and gradually recovered in several hundred nano-seconds. This phase change is due to the layer-beam bombardment of covalent electrons,which makes the covalent electron density redistribute.

Keywords: X-ray diffraction, phase problem, time-resolved