X-RAY-INDUCED ULTRAFAST MANY BODY PHYSICS

这个子项目是利用资源的许多研究子项目之一。 由NIH/NCRR资助的中心拨款提供。对子项目的主要支持 子项目的首席调查员可能是由其他来源提供的， 包括美国国立卫生研究院的其他来源。为子项目列出的总成本可能 表示该子项目使用的中心基础设施的估计数量， 不是由NCRR赠款提供给次级项目或次级项目工作人员的直接资金。 用聚焦的粉色光束可以在半导体靶上获得极高的X射线密度。由此产生的多体响应将主要通过测量波段边缘附近的光学吸收以及可能的光学反射率来探测。粉色光束每飞秒可发射多达105个X射线光子。当聚焦在所选择的束线上时，吸收位的瞬时密度约为1012 cm-3。虽然这与传统的半导体掺杂密度相比较低，但这种深核心空穴的浓度将产生许多身体响应的级联：频带狭窄的光电子、俄歇电子、X射线荧光、每个X射线的数千个电子-空穴对光子、电子-等离子体相互作用、电子-声子相互作用等。在本X射线泵浦/光学探针研究中，将使用皮秒激光脉冲进行带边吸收测量。这可能是探索半导体的第一个同步加速器研究，许多身体对硬x射线的反应是越来越多的人对使用高x射线能量密度来探索凝聚态物理的兴趣的一部分。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Extremely high x-ray densities in a semiconductor target will be obtained with a focused pink beam. The resultant many-body response will be probed primarily by measuring optical absorption near the band edge as well as optical reflectivity when possible. A pink beam will deliver up to 105 x-ray photons per femtosecond. When focused at the selected beamline on a GaAs target the instantaneous density of absorption sites is ~1012 cm-3. While this is low compared to traditional semiconductor doping densities this concentration of deep core holes will generate a cascade of many body responses: band-narrowing photoelectrons Auger electrons x-ray fluorescence thousands of electron-hole pairs per x-ray photon electron-plasmon interactions electron-phonon interactions etc. Band-edge absorption measurements will be made with picosecond laser pulses in this x-ray pump/optical probe study. This is perhaps the first synchrotron study to explore semiconductor many body responses to hard x-rays part of the vanguard of increasing interest in using high x-ray energy densities to explore condensed matter physics.