RUI: Understanding and Control of Strong-Field Molecular Ionization

自从20世纪60年代激光发明以来，科学家们一直试图利用激光直接影响化学反应。在这种情况下，激光脉冲可以被认为是一种驱动化学反应的新型试剂。该项目将通过制作此类反应产物的三维图像来推进激光辅助化学反应的研究。这门科学可以为经济和公众福利做出贡献，因为这些基于激光的试剂的发展有一天可以让新材料和药物的化学合成成为可能。然而，实现这一目标的进展是具有挑战性的，因为分子是如此复杂和动态，很难确定正确的激光特性来驱动特定的过程。该项目将使用实验反馈来指导对可能的激光脉冲的自适应搜索。这种类型的方法被证明是有效的，但它只与驱动它的反馈一样好。这些研究的目标是开发和利用增强的基于图像的反馈技术，以改进这种控制化学动力学的方法。与本科生一起做这项工作还可以为学生提供进一步科学教育的动力，从而有助于培养高技能的劳动力。强激光场与多原子分子之间的相互作用是超快科学许多方面的前沿。成形的超快激光脉冲可以有力地影响分子动力学，从而允许获得其他方法通常无法获得的结果。本研究计划的重点领域是自适应飞秒控制，其中使用学习算法来指导形状超快激光脉冲的构建，以产生期望的结果。为了使自适应搜索成功，需要鲁棒的、定义良好的反馈。为此，该团队开发了使用激光分子反应产物的三维动量成像的能力。通过应用基于快速三维图像的反馈来控制小碳氢化合物分子的光异构化，该团队能够研究如何操纵分子的电子激发影响核运动，从而影响超快化学过程。了解基本的强场过程有助于指导这些一致的控制协议，允许该团队将基于图像的反馈链接到特定的目标状态。该团队将进行几个实验，以促进对多原子系统中强场电离如何发生的理解，包括具有强里德伯特征的场盛装轨道在多原子分子中隧穿电离中的作用。

Ever since the development of the laser in the 1960's, scientists have sought to use lasers to directly influence chemical reactions. In this context, a pulse of laser light can be thought of as a new type of reagent that drives a chemical reaction. This project will advance the study of laser-assisted chemical reactions by making three-dimensional images of the products of such reactions. This science can contribute to the economy and to public well-being because development of these laser-based reagents could one day allow chemical synthesis of novel materials and medicines. Progress toward this goal is challenging, however, because molecules are so complicated and dynamic that it is difficult to determine the correct laser characteristics to drive a particular process. This project will use experimental feedback to guide an adaptive search of the possible laser pulses. This type of method is proven to work, but it is only as good as the feedback that drives it. The goal of these studies is to develop and exploit enhanced image-based feedback techniques that refine this approach to controlling chemical dynamics. Doing this work with undergraduate students also provides students with motivation for further scientific education and therefore helps develop a highly skilled workforce. Interactions between strong laser fields and polyatomic molecules are at the forefront of many aspects of ultrafast science. Shaped ultrafast laser pulses can powerfully influence molecular dynamics, thus allowing access to outcomes not typically available by other means. The area of emphasis of this research program is adaptive femtosecond control, in which a learning algorithm is used to guide the construction of shaped ultrafast laser pulses that produce a desired result. In order for the adaptive search to succeed, robust, well-defined feedback is required. To this end, this team developed the capacity to use three-dimensional momentum imaging of the laser-molecule reaction products. By applying rapid three-dimensional image-based feedback to the control of photoisomerization in small hydrocarbon molecules, this team is able to examine how manipulating the electronic excitation of the molecule influences the nuclear motion, and thus affects ultrafast chemical processes. Understanding basic strong-field processes helps to guide these coherent control protocols by allowing this team to link image-based feedback to specific target states. This team will pursue several experiments that can advance the understanding of how strong-field ionization occurs in polyatomic systems, including the role that field-dressed orbitals with strong Rydberg character have on tunneling ionization in polyatomic molecules.