Strong-Field and Ultrafast Processes

本项目旨在描述强相干辐射与大量子系统的相互作用，并利用超快外场对原子中相关的动态电子过程进行成像和控制。对这些过程进行理论描述的挑战在于难以准确地描述包括强振荡场在内的粒子间随时间变化的相互作用。该项目支持的基础研究将提供对光化学过程的见解，并为在原子尺度上控制物质的努力做出广泛贡献。参与该项目的博士后研究人员将接受理论原子、分子和光学物理、计算物理和超冷原子物理的广泛教育；在科学传播的各个方面的第一手经验，以及在大型十大赠地大学教授本科生的第一手经验。此外，这项工作将有助于扩大STEM教育的参与，因为PI是一个代表性不足的少数群体，将成为代表性不足群体学生的榜样。强场物理中的时间相关研究将促进对非线性和相关基本过程的理解，如双活性电子原子系统的非顺序双电离（NSDI）和阈值以上电离（ATI）。本项目支持的具体研究包括通过调整延迟IR和XUV场的参数来完全控制He原子的NSDI中的特定通道。从ATI中控制光电子波包导致螺旋涡表明了它的相干性（波）性质，这将在几个科学分支中发生，这里在冷原子物理学中进行了说明。通过模拟超冷原子物理中螺旋涡的基本模式，本研究试图建立超冷原子量子模拟器，作为研究超快动力学的补充工具，不仅适用于小型量子系统，也适用于大型量子系统。为了克服上述挑战，该计划旨在开发一些理论时间相关方法（超越单活性电子近似）。特别是，对于双电子系统，该小组开发了高效，优化和精确的数值方法来解决全维时间相关Schrödinger方程。对于更大的量子系统，他们建议使用超冷原子量子模拟器，这里将对单电子和双电子原子的情况进行说明，作为原理计算的证明。UCSB的David Weld最近的实验开发突出了这个项目的迫切需求和及时性。该项目由原子、分子和光学物理理论项目和促进竞争研究的既定项目（EPSCoR）共同资助。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project aims to describe the interaction of intense coherent radiation with large quantum systems, and to image and control the correlated dynamical electronic processes in atoms by using ultrafast external fields. The challenge in the theoretical description of such processes resides in the difficulty in describing accurately the time-dependent interactions between particles including the strong oscillatory fields. The basic research supported by this project will provide insights into photochemical processes and contribute broadly towards efforts to control matter on an atomic scale. A postdoctoral researcher involved with this project will be given a broad education in theoretical atomic, molecular, and optical physics, in computational physics, and in ultra-cold atom physics; first-hand experience in all aspects of scientific communication, and in teaching undergraduates at a large Big 10 Land Grant university. In addition, this work will contribute to broadening participation in STEM education since the PI, an underrepresented minority, will serve as a role model for students from underrepresented groups.The time-dependent studies in strong-field physics will promote the understanding of nonlinear and correlated elementary processes, such as non-sequential double ionization (NSDI) and above-threshold ionization (ATI) of two-active-electron atomic systems. Specific investigations supported in this project include a full control of a particular channel in NSDI of He atoms by tuning parameters of the time-delayed IR and XUV fields. Control of photoelectron wave packets leading to spiral vortices from ATI demonstrates its coherence (wave) nature, which is expected to occur in several branches of science, is illustrated here in cold-atom physics. By emulating the basic pattern of spiral vortices in ultracold-atom physics, this research seeks to establish ultracold-atom quantum simulators as a complementary tool for investigating ultrafast dynamics not only for small but also for larger quantum systems. To overcome the challenge described above, this program aims to develop some theoretical time-dependent approaches (that go beyond the single-active-electron approximation). In particular, for two-electron systems the group has developed efficient, optimized, and accurate numerical methods to solve the full-dimensional time-dependent Schrödinger equation. For larger quantum systems, they propose to use ultracold-atom quantum simulators, which will be illustrated here for the case of one- and two-electron atoms as proof-of-principle calculations. The recent experimental development by David Weld from UCSB highlighted the critical need for and timeliness of this project.This project is jointly funded by the Atomic, Molecular, and Optical Physics Theory Program and the Established Program to Stimulate Competitive Research (EPSCoR).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.