Coherent X-ray diffraction patterns were recorded by using an X-ray free-electron laser to illuminate barium titanate nanocrystals as a function of time delay after laser excitation. Rather than seeing any significant thermal expansion effects, the diffraction peaks were found to move perpendicular to the momentum transfer direction. This suggests a laser driven rotation of the crystal lattice, which is delayed by the aggregated state of the crystals. Internal deformations associated with crystal contacts were also observed.

中文翻译：

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光学激发钛酸钡纳米晶体的异常呼吸行为

通过使用X射线自由电子激光记录钛酸钡纳米晶体作为激光激发后时间延迟的函数，记录了相干的X射线衍射图。没有看到任何明显的热膨胀效应，而是发现衍射峰垂直于动量传递方向移动。这表明由激光驱动的晶格旋转，由于晶体的聚集状态而延迟。还观察到与晶体接触有关的内部变形。