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.

我们利用皮秒时间分辨x射线衍射技术研究了脉冲激发引起的相变动力学。脉冲x射线是通过在真空室中将飞秒激光束聚焦在10^17 W/cm^2的金属目标上产生的，并从Be窗口提取。用L-N_2冷却的x射线电荷耦合器件检测x射线衍射后的衍射结果。使用泵和探针技术进行时间分辨测量。用功率密度为3.3 GW/cm^2的300-ps激光束照射样品进行激发。所用样品为硅晶体（Si(111)）。每隔50 ps获得时间分辨x射线衍射，时间分辨为10 ps。直接观察到晶格变形对应于激光加热和声子传播，随后能量从电子系统转移到晶格系统。为了提高样品位置的x射线强度，利用约翰逊弯曲晶体构建了x射线聚焦系统。x射线聚焦在直径为100·m、强度为400倍的光斑上。新建立的x射线衍射系统可在现场观测约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。

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)

K.G.Nakamura、K.Wakabayashi、Y.Hironaka、K.Kondo：“冲击压缩状态的泵和探针测量”J.Phys。