Dynamics of structural phase transition studied by picosecond time-resolved X-ray diffraction

通过皮秒时间分辨 X 射线衍射研究结构相变动力学

• 批准号: 13450265
• 负责人: KONDO Ken-ichi
• 金额: $ 9.22万
• 依托单位: Tokyo Institute of Technology
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2001
• 资助国家: 日本
• 起止时间: 2001 至 2002
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-13450265/
• 关键词: time-resolved X-ray diffraction; femtosecond laser; pulsed X-rays; pump and probe; dynamics; phase transition; レーザー吸収; X線回折; 時間分解測定; シリコン; オージェ再結合; プラズマ臨界密度; 衝撃波

We investigated dynamics of a phase transition, which is induced by impulsive excitation, using a picosecond time-resolved X-ray diffraction technique. The pulsed X-rays were generated by focusing femtosecond laser beams onto metal targets at 10^17 W/cm^2 in a vacuum chamber, and extracted from a Be window. The X-rays were directed to a sample and the diffracted X-rays were detected by the L-N_2 cooled X-ray charge-coupled device. Time-resolved measurements were performed using a pump and probe technique. A 300-ps laser beam was irradiated on the sample at power density of 3.3 GW/cm^2 for excitation. The sample used was a silicon crystal (Si(111)). The time-resolved X-ray diffraction was obtained every 50 ps of time interval with a time-resolution of 10 ps. Lattice deformation corresponds to laser heating and acoustic-phonon propagation, which followed by the energy transfer from an electronic system to a lattice system, was directly observed. In order to increase the X-ray intensity at the sample position, an X-ray focusing system was constructed using a Johansson curved crystal. The X-rays were focused at a spot size with a diameter of 100・m and 400-times higher intensity. The newly constructed X-ray diffraction system can observe approximately 4 degrees at the spot.

我们研究了使用皮秒时间分辨X射线衍射技术，研究了相变的动力学，该动力学是由冲动兴奋引起的。脉冲X射线是通过将飞秒激光束聚焦在真空室中10^17 W/cm^2的金属靶标上产生的，然后从BE窗口中提取。将X射线定向到样品，并通过L-N_2冷却的X射线电荷耦合器件检测到衍射的X射线。使用泵和探针技术进行时间分辨测量。在样品上以3.3 GW/cm^2的功率密度在样品上照射300-PS激光束，以进行兴奋。所使用的样品是硅晶体（SI（111））。每50 ps的时间间隔获得时间分辨X射线衍射，时间分辨率为10 ps。直接观察到了晶格变形对应于激光加热和声音传播，然后直接观察到从电子系统到晶格系统的能量转移。为了增加样品位置的X射线强度，使用Johansson弯曲晶体构建了X射线聚焦系统。 X射线的聚焦为斑点大小，直径为100°m，强度高400倍。新建的X射线衍射系统可以在现场观察到大约4度。

项目成果

H.Kishimura, A.Yazaki, H.Kawano, Y.Hironaka, K.G.Nakamura, K.Kondo: "Picosecond structural dynamics in photoexcited Si probed by time-resolved x-ray diffraction"J.Chem.Phys.. 117. 10239-10243 (2002)

H.Kishimura、A.Yazaki、H.Kawano、Y.Hironaka、K.G.Nakamura、K.Kondo：“通过时间分辨 X 射线衍射探测光激发 Si 中的皮秒结构动力学”J.Chem.Phys.. 117. 10239

H. Kishimura, A. Yazaki, Y. Hironaka, K.G. Nakamura, and K. Kondo: "Lattice deformation of laser-irradiated silicon crystal studied by picosecond X-ray diffraction"Appl. Surf. Sci. 207. 314-317 (2003)

H. Kishimura、A. Yazaki、Y. Hironaka、K.G.

H.Kishimura, A.Yazaki, Y.Hironaka, K.G.Nakamura, K.Kondo: "Lattice deformation of laser-irradiated silicon crystal studied by picosecond X-ray diffraction"Appl.Surf.Sci.. 207. 314-317 (2003)

H.Kishimura、A.Yazaki、Y.Hironaka、K.G.Nakamura、K.Kondo：“通过皮秒 X 射线衍射研究激光照射硅晶体的晶格变形”Appl.Surf.Sci.. 207. 314-317 (2003)

K.G. Nakamura, K.Wakabayashi, Y.Hironaka, K. Kondo: "Pump and probe measurements of shock compressed states"J. Phys. : Condens. Matter. 14. 10817-10820 (2002)

公斤。

H.Kishinrura, A.Yazaki, Y.Hironaka, K.G.Nakamura, K.Kondo: "Lattice deformation of laser-irradiated silicon crystal studied by picosecond X-ray diffraction"Appl.Surf.Sci.. 207. 314-317 (2003)

H.Kishinrura、A.Yazaki、Y.Hironaka、K.G.Nakamura、K.Kondo：“通过皮秒 X 射线衍射研究激光照射硅晶体的晶格变形”Appl.Surf.Sci.. 207. 314-317 (2003)