RUI: Understanding and Control of Strong-Field Molecular Ionization

自从20世纪60年代激光发展以来，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。 该项目将通过制作激光辅助化学反应产物的三维图像来推进此类反应的研究。 这门科学可以为经济和公众福祉做出贡献，因为这些基于激光的试剂的发展有朝一日可能会允许化学合成新材料和药物。 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，以至于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，但它只和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，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也为学生提供了进一步科学教育的动力，因此有助于培养高技能的劳动力。 强激光场和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，从而获得其他手段通常无法获得的结果。 该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产生所需结果的成形超快激光脉冲的构建。 为了使自适应搜索成功，需要鲁棒的、定义明确的反馈。 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。通过将快速的基于三维图像的反馈应用于小烃分子中光异构化的控制，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，使该团队能够将基于图像的反馈与特定的目标状态联系起来。 该团队将进行几项实验，以促进对强场电离如何在多原子系统中发生的理解，包括具有强里德伯特征的场修饰轨道对多原子分子中隧道电离的作用。

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.