Non-Adiabatic Dynamics in Molecules Driven by Strong Laser Fields

Weinacht教授和他的研究生和本科生研究团队将开发和使用超快脉冲高功率激光器来研究分子中电子和原子核的运动。观察这种运动将增进我们对电子和原子核协同作用的许多自然过程的理解，包括视觉、能量存储、能量转换和化学转换。了解这些动力学对于太阳能电池、超快分子开关和量子计算机等新技术的发展也很重要。虽然激光是操纵和测量分子中电子的天然工具，但人们需要非常短的激光脉冲才能实时操纵电子。该项目中的研究人员将使用超短激光脉冲(强度远大于太阳表面，持续时间不到万亿分之一秒！)以电离分子，移除与分子结合的众多电子中的一个。当电子离开分子时，他们将利用一种名为“速度图成像”的技术来拍摄电子的照片。这些图像可以用来理解电离过程中电子和原子核的耦合动力学，这对于理解化学动力学和发展高速电子很重要。为了跟踪分子中的非绝热动力学，实验工作将发展脉冲形状光谱。这项工作将比较使用整形超快激光脉冲测量强场分子电离与更传统的激发态动力学泵浦探测测量。这两种方法包含关于耦合电子核动力学的互补信息，可以通过与测量观测数据的计算进行详细比较来揭示这些信息。这项工作将加深我们对分子中非绝热动力学的理解。该小组最近的测量结果强调了利用整形激光脉冲控制内部转换的能力。这使得该小组能够通过内部转换跟踪电子相干的演变，并测量一系列卤化甲烷分子的相干时间。该小组将把这些测量扩展到一系列新的有机环分子，即吡咯、呋喃和噻吩类分子，并将这些测量结果与该小组实验室中的时间分辨光电子能谱测量结果进行比较。这将使该小组能够开发脉冲形状光谱学作为跟踪电子和核动力学的强大工具，并在与理论比较和补充实验的基础上进行严格的解释。该奖项反映了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。

Professor Weinacht and his research team of graduate and undergraduate students will develop and use ultrafast-pulse high-power lasers to study the motion of electrons and nuclei in molecules. Observing such motion will advance our understanding of many natural processes in which the electrons and nucleus act in concert, including vision, energy storage, energy conversion, and chemical transformation. Understanding these dynamics is also important for the development of new technologies such as solar cells, ultrafast molecular switches, and quantum computers. While lasers are natural tools for manipulating and measuring electrons in molecules, one requires very short laser pulses in order to manipulate electrons in real time. The investigators in this project will use intense ultrashort laser pulses (with intensities far greater than at the surface of the sun, and durations of less than a hundredth of a trillionth of a second!) in order to ionize molecules, removing one of the many electrons bound to the molecule. They will take pictures of the electrons as they come off the molecules, making use of a technique called 'velocity map imaging'. These pictures can be used to understand the coupled dynamics of electrons and nuclei during ionization, which is important for understanding chemical dynamics and for developing high speed electronics.The experimental work will develop pulse shape spectroscopy in order to follow nonadiabatic dynamics in molecules. The work will compare measurements of strong field molecular ionization using shaped ultrafast laser pulses with more traditional pump probe measurements of excited state dynamics. The two approaches contain complementary information on coupled electron nuclear dynamics, which can be uncovered via detailed comparisons with calculations of the measurement observables. The work will deepen our understanding of nonadiabatic dynamics in molecules. Recent measurements from the group have highlighted the ability to control internal conversion with shaped laser pulses. This allowed the group to follow the evolution of electronic coherence through internal conversion and measure the coherence time for a series of halogenated methane molecules. The group will extend these measurements to a new family of organic ring molecules, pyrrole, furan and thiophene, and compare the measurements with time resolved photoelectron spectroscopy measurements made in the group's laboratory. This will allow the group to develop pulse shape spectroscopy as a powerful tool for following electronic and nuclear dynamics with a rigorous interpretation based on comparison with theory and complementary experiments.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.