RUI: Photoinduced Ultrafast Relaxation, Ionization, and Impact-Induced Positronium Formation of Fullerene Class of Molecules

RUI：富勒烯类分子的光诱导超快弛豫、电离和碰撞诱导正电子形成

• 批准号: 2110318
• 负责人: HIMADRI CHAKRABORTY
• 金额: $ 18万
• 依托单位: Northwest Missouri State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-08-15 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2110318&HistoricalAwards=false
• 关键词: RUI; Photoinduced; Ultrafast; Relaxation; Ionization

By shining laser light on a molecule, one can probe the molecule’s response to radiation and the molecule’s successive relaxation processes. This is a powerful scientific method to learn fundamental properties of materials and is therefore beneficial for the progress of basic science and applied technology. The molecules to be studied in the current research program are Buckminster fullerenes and larger fullerenes, including atoms/clusters caged inside these molecules (endofullerenes), and polymerized fullerenes. These materials hold the promise of exciting applications in areas including quantum computations, superconductivity, biomedical fields, drug delivery research, magnetic resonance imaging, molecular devices, energy storage, conversion and organic photovoltaics. Hence, understanding the physical/chemical structure and response properties of these systems are matters of great scientific interest. Using large scale, high performance computer simulations the program aims to investigate in real time these molecular processes. Investigations will be performed to learn how electrons inside the system individually couple to the molecule’s vibration, collectively interact with each other to move/relax internally or exit the system, and the role that structure, geometry, and internal energy distribution of the system plays in each mechanism. As an interesting component of the research, plans are in place to test some of these spectroscopic properties by colliding fullerene materials with positrons, the exotic antiparticles of electrons. Undergraduate students are involved to enhance their educational experience and motivate them for physics/science careers. The project includes the following detailed studies: I) Photoinduced charge transfer (CT) is a key process in organic photovoltaics. The strong coupling of ionic and electronic degrees of freedom drives these ultrafast processes. Frameworks based on nonadiabatic molecular dynamics are appropriate for providing accurate, comprehensive descriptions of the underlying mechanism. Using high-performance computational methodology, the group plans to simulate and study relaxation processes in selected endofullerenes to motivate experiments. Initial photoexcitations within the confined atom, or the confining fullerene, or from-atom-to-fullerene “transfer” excitations will be considered. Repeated intermediate CTs causing the electron to toggle between the atom and the fullerene, including transient delay events, during the relaxation will be followed in real time. This track of research opens a new subfield of ultrafast chronoscopy. II) Attosecond photoemission calculations and studies of fullerenes and endofullerenes. This line of research will dovetail well with active research in ultrafast AMO, where novel attosecond laser pulses have enabled precision studies of light-matter interactions. III) Inter-Coulombic decay (ICD) is a nonradiative relaxation of a vacancy in a cluster and a topic of contemporary interest. Endofullerenes, being asymmetric dimers of concentric systems, can induce novel ICDs. The planned studies on ICDs in cluster-endofullerenes can predict fundamental effects and drive experiments. V) Positronium (Ps) formation following the impact of positrons on matter. The science to be learned from the study of Ps formation from fullerenes/endofullerenes at plasmon resonance energies will usher new directions of Ps spectroscopy, spawning 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.

通过将激光照射到分子上，可以探测分子对辐射的响应以及分子的连续弛豫过程，这是了解材料基本科学性质的有力方法，因此有利于分子基础科学和应用技术的进步。当前研究计划要研究的是巴克明斯特富勒烯和更大的富勒烯，包括笼在这些分子内的原子/簇（内富勒烯），以及聚合富勒烯，这些材料有望带来令人兴奋的结果。其在量子计算、超导、生物医学领域、药物输送研究、磁共振成像、分子器件、能量存储、转换和有机光伏等领域的应用因此，了解这些系统的物理/化学结构和响应特性具有重大的科学意义。该项目旨在使用大规模、高性能计算机模拟来实时研究这些分子过程，以了解系统内的电子如何单独耦合到分子的振动，以及如何相互相互作用以在内部移动/松弛。或者退出系统，以及系统的结构、几何形状和内部能量分布在每种机制中发挥的作用作为研究的一个有趣组成部分，计划通过富勒烯材料与正电子的碰撞来测试其中一些光谱特性，该项目包括以下详细研究：I）光致电荷转移（CT）是有机光伏耦合的关键过程。离子和电子自由度驱动这些超快过程，基于非绝热分子动力学的框架适合于提供底层机制的准确、全面的描述，该小组计划使用高性能计算方法来模拟和研究选定的内富勒烯的弛豫过程。为了激发实验，将考虑限制原子内的初始光激发，或限制富勒烯，或从原子到富勒烯的“转移”激发，从而导致电子。原子和富勒烯之间的切换，包括瞬态延迟事件，将在弛豫过程中实时跟踪，这将开辟超快计时学的新子领域 II) 阿秒光发射计算和富勒烯和内富勒烯的研究。研究将与超快 AMO 的积极研究紧密结合，其中新型阿秒激光脉冲使得光与物质相互作用的精确研究成为可能。 III) 库仑间衰变 (ICD)。内富勒烯是团簇中空位的非辐射弛豫，是当代感兴趣的主题，它是同心系统的不对称二聚体，可以诱导新型 ICD。计划对团簇内富勒烯中的 ICD 进行研究可以预测基本效应并推动实验。正电子对物质的影响后形成正电子 (Ps) 通过研究等离子体激元中富勒烯/内富勒烯的 Ps 形成而学到的科学知识。共振能量将引领 Ps 光谱、产卵实验的新方向。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

A dynamical (e,2e) investigation into the ionization of pyrazine

• DOI: 10.1016/j.cplett.2021.139000
• 发表时间: 2021-10
• 期刊: Chemical Physics Letters
• 影响因子: 2.8
• 作者: Darryl B Jones;E. Ali;H. Chakraborty;C. Ning;G. García;D. Madison;M. Brunger