RUI: Strong-Field Control of Intramolecular Dynamics in Polyatomic Molecules

原子可以从光中吸收能量，这一过程激发了它们的电子。 当由多个原子组成的分子以类似的方式吸收光时，吸收的能量可以迅速从电子转移出去，并导致分子内的原子移动。 分子可以通过拉伸或弯曲而振动，或者分子中的原子可以围绕彼此旋转。 这种行为是视觉或光合作用等过程的关键步骤，了解这种能量转移是如何完成的可以帮助设计更有效的光收集或构建光激活分子开关。 在极端水平上，强超短激光脉冲可以直接操纵瞬态分子结构。 换句话说，激光脉冲的精确应用可以被认为是以期望的方式改变化学过程的基于光的试剂。 由于这些原因，这项基础研究探索了光如何激发分子中的电子，从而导致瞬态分子结构的变化，并寻求控制这些过程的方法。 这些研究是在本科生中完成的，这为进一步的科学教育提供了动力，因此有助于培养高技能的劳动力。这项研究使用动量成像方案来测量在应用强超快激光脉冲后分子的结构演变。 光电子圆二色性是分子中手性结构的灵敏探针，本研究的一部分目的是利用光电子圆二色性信号来探测激光诱导的从非手性结构到手性结构的转变。 符合离子动量成像可以识别分子中特定的动力学过程，多粒子累积量分析可以比传统的符合分析提高几个数量级的数据采集速率。 开发这种检测方法是本研究的第二个主要目标。 然后，这两种检测方案都可以与超快激光脉冲整形相联系，并通过开环或闭环控制方案来探索分子动力学的相干控制。 这些研究探索了分子中电子与核耦合的基本问题以及如何控制这些过程。该奖项反映了NSF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。

Atoms can absorb energy from light, a process that excites their electrons. When molecules, which are composed of multiple atoms, absorb light in a similar manner, the absorbed energy can quickly be transferred away from the electrons and cause the atoms within the molecule to move. The molecules can vibrate by stretching or bending, or the atoms in the molecule can rotate about each other. This sort of behavior is a key step in processes such as vision or photosynthesis, and understanding how this energy transfer is accomplished can help design more efficient collection of light or to construct light-activated molecular switches. At an extreme level, intense, ultrashort laser pulses can manipulate transient molecular structure directly. Stated another way, the precise application of a laser pulse can be thought of as a light-based reagent that alters a chemical process in a desired manner. For these reasons, this basic research explores how the excitation of electrons in molecules by light leads to changes in transient molecular structure and seeks ways of controlling those processes. These studies are done with undergraduate students, which provides motivation for further scientific education and therefore helps develop a highly skilled workforce.This research uses momentum imaging schemes to measure the structural evolution of molecules following the application of intense, ultrafast laser pulses. Photoelectron circular dichroism is a sensitive probe of chiral structure in molecules and one part of this research aims to use these signals to probe laser-induced transitions from achiral to chiral structures. Coincidence ion momentum imaging can identify specific dynamic processes in molecules, and multi-particle cumulant analysis can increase the data acquisition rate by orders of magnitude over traditional coincidence analysis. Developing this detection approach is the second main goal of this research. Both detection schemes can then be linked to ultrafast laser pulse shaping and used to explore coherent control of molecular dynamics, either through open- or closed-loop control schemes. These studies explore fundamental questions about electronic to nuclear coupling in molecules and how these processes might be controlled.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.