Collaborative Research: Probing Attosecond Electron Correlation in Atoms

合作研究：探测原子中的阿秒电子相关性

• 批准号: 1068604
• 负责人: Zenghu Chang
• 金额: $ 57万
• 依托单位: The University of Central Florida Board of Trustees
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-08-01 至 2015-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1068604&HistoricalAwards=false
• 关键词: Collaborative; Research; Probing; Attosecond; Electron

The time scale of electron dynamics in matter is represented by the atomic unit of time, which is 24 attoseconds. Although isolated attosecond photon pulses were demonstrated in 2001, few laboratories have been able to own the new light source because the generation technique is very difficult. Furthermore, the existing attosecond source is not strong enough for performing attosecond pump/attosecond probe experiments. In the last five years, Chang's group has developed a technique, Double Optical Gating (DOG), which can generate isolated attosecond pulses rather easily. It also allows the up-scaling of attosecond pulse energy. With the current support from the National Science Foundation, Chang's experimental group and Hu's theoretical group work together to understand and control ultrafast electron-electron interaction in the time domain by taking advantage of the attosecond source based on the DOG scheme. We focus on the autoionization of atoms as it is dominated by the electron correlation. As the starting point, the two-electron system, helium, is chosen as the target. Unlike spectral-domain experiments performed in the past using synchrotron light, helium atoms are pumped from the ground state into either continuum states or doubly-excited states by isolated attosecond XUV pulses. The instantly-initiated electron-correlations in the doubly-excited states, their subsequent fast decay and the interference with the continuum states, are then probed either by another time-delayed attosecond XUV pulse or by an intense few-cycle near infrared (NIR) laser pulse. The attosecond probe pulse would "freeze" the motion of the two electrons and "map-out" in real time the ultrafast electron-correlation dynamics. The strong NIR field can modify the electron-electron interactions within a fraction of an optical cycle in order to manipulate and control the ultrafast electron correlations. The experiment-theory collaboration allows experimental benchmarking of the quantum-mechanical ab initio calculations, laying a foundation for studying electron dynamics in more complex atoms and molecules. Electron-electron interactions play an essential role in a wide range of fundamentally important many-body phenomena in modern chemistry, physics and biology. The broad impacts of this program are two-fold. First of all, developing tools for observing electron dynamics with an unprecedented time resolution will lead to new insights into the fundamental questions of how electron correlation plays a role in molecular structure formation. Such insights will particularly help chemists to understand electron correlations in chemical reactions better. Secondly, finding techniques to control electron dynamics with external fields can significantly advance the technologies for manipulating complex systems and chemical reactions at the fundamental electronic level. Moreover, the new attosecond light source under development can spur a revolution in ultrafast free-space communication and biomolecule imaging. The program supports three students to work at one of the most exciting forefronts of the physics. They are trained to become leaders in this new research field and experts of the next generation technologies. The experiments are conducted at the Florida Attosecond Science and Technology (FAST) laboratory, which was newly established at the University of Central Florida. A course on attosecond optics and another one on attosecond physics are offered by Chang for undergraduate and graduate students who use the attosecond facility for lab demonstrations.

物质中电子动力学的时间尺度由时间的原子单位表示，即24个attsonds。尽管在2001年证明了孤立的Attsond光子脉冲，但由于发电技术非常困难，因此很少有实验室能够拥有新的光源。此外，现有的Attosend来源不足以执行Attosond Pump/Attosond探针实验。在过去的五年中，Chang的小组开发了一种技术，即双光门控（Dog），可以很容易地产生孤立的Attosent脉冲。它还允许对Attosend脉冲能量进行更高的规模。在国家科学基金会目前的支持下，Chang的实验组和HU的理论组共同努力，通过基于狗方案利用Attosond Source来理解和控制时间域中的超快电子 - 电子相互作用。我们专注于原子的自由度，因为它由电子相关性主导。 作为起点，选择两个电子系统氦气作为目标。与过去使用同步加速器光进行的光谱域实验不同，氦原子是通过孤立的attosecond Xuv脉冲将氦原子从基态泵送到连续状态或双激发状态的。然后，另一个耗时的attosecond Xuv脉冲或在红外线（NIR）激光脉冲附近的激烈的几个循环脉冲中探测了双兴趣状态，随后的快速衰减和对连续态的干扰的即时电子相关。 Attsond探针脉冲将实时“冻结”两个电子的运动和“ map-out”。超快电子相关动力学。强的NIR场可以在光周期的一部分内修改电子电子相互作用，以操纵和控制超快电子相关性。实验理论的协作允许对量子力学的从头算计算进行实验基准测试，为研究更复杂的原子和分子中的电子动力学奠定了基础。电子电子相互作用在现代化学，物理学和生物学的各种根本重要的多体现象中起着至关重要的作用。该计划的广泛影响是两个方面。首先，开发以前所未有的时间分辨率观察电子动力学的工具将导致对电子相关性如何在分子结构形成中起作用的基本问题的新见解。这种见解将特别有助于化学家更好地了解化学反应中的电子相关性。其次，找到用外场控制电子动力学的技术可以显着推进在基本电子水平下操纵复合系统和化学反应的技术。此外，开发中的新的Attsond Light源可以刺激超快自由空间通信和生物分子成像中的一场革命。该计划支持三个学生在物理学中最令人兴奋的前沿之一工作。他们受过培训，成为这个新研究领域的领导者和下一代技术的专家。 这些实验是在佛罗里达州的科学技术（Fast）实验室进行的，该实验室是在佛罗里达州中部新成立的。 Chang为使用AttoSecond设施进行实验室示范的本科生和研究生提供了有关Attosecond Optics的课程和Attosecond物理学的另一项课程。