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

原子可以从光中吸收能量，这是一个激发电子的过程。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来振动，或者分子中的原子可以相互旋转。这种行为是视觉或光合作用等过程中的关键一步，了解这种能量转移是如何完成的，有助于设计更有效的光收集或构建光激活的分子开关。在极端水平上，强的超短激光脉冲可以直接操纵瞬时分子结构。换句话说，激光脉冲的精确应用可以被认为是一种以所需方式改变化学过程的光基试剂。出于这些原因，这项基础研究探索了光激发分子中的电子如何导致瞬时分子结构的变化，并寻找控制这些过程的方法。这些研究是在本科生中进行的，这为进一步的科学教育提供了动力，因此有助于培养一支高技能的劳动力队伍。这项研究使用动量成像计划来测量在应用强、超快激光脉冲后分子结构的演变。光电子圆二色谱是分子中手性结构的灵敏探针，本研究的目的之一是利用这些信号探测激光诱导的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，而多粒子累积量分析可以比传统的符合分析提高数据采集速度几个数量级。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，用于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的耦合以及如何控制这些过程的基本问题。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.