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.

通过在分子上发光激光，可以探测该分子对辐射的反应以及分子成功的松弛过程。这是一种学习材料基本特性的强大科学方法，因此对基础科学和应用技术的进步有益。在当前的研究计划中要研究的分子是Buckminster Fullerenes和较大的富勒烯，包括在这些分子内（Endofullererenes）内笼罩的原子/簇，以及聚合富勒烯。这些材料有望在包括量子计算，超导性，生物医学领域，药物递送研究，磁共振成像，分子设备，能源存储，转换和有机光伏的领域中进行令人兴奋的应用。因此，了解这些系统的物理/化学结构和响应特性是极大的科学利益。该程序旨在实时研究这些分子过程。将进行调查，以了解系统内部的电子如何单独将分子的振动与彼此相互交互以在内部移动/放松，以及系统在每种机制中扮演的结构，几何形状和内部能量分布的作用。作为研究的一个有趣组成部分，已经制定了计划，通过用阳性材料（电子产品的异国情调的反extricticles碰撞富勒烯材料）来测试其中一些光谱性能。本科生参与以增强他们的教育经验并激励他们从事物理/科学职业。该项目包括以下详细研究：i）光诱导的电荷转移（CT）是有机光伏的关键过程。离子和电子自由度的强耦合驱动这些超快过程。基于非绝热分子动力学的框架适合提供基本机制的准确，全面的描述。该小组计划使用高性能计算方法，以模拟和研究选定的内叶烯中的放松过程，以进行动机实验。将考虑在受限原子或限制的富勒烯或从原子到实心的“转移”兴奋中的初始光呼应。重复的中间CTS导致电子在放松期间的原子和富勒烯之间切换，包括瞬态延迟事件。这项研究的轨迹开辟了一个超快计时镜检查的新子场。 ii）富勒烯和内叶烯烯的光发射计算和研究。这项研究将与超快AMO的积极研究相吻合，在该研究中，新型的Attosond激光脉冲已实现了对光 - 物质相互作用的精确研究。 iii）肺地衰变（ICD）是集群中空缺的非赋权放松，也是当代兴趣的话题。内叶烯是同心系统的不对称二聚体，可以诱导新颖的ICD。群集 - 尾列烯烯中ICD的计划研究可以预测基本效果并驱动实验。 v）阳性对物质的影响后的正电子（PS）形成。从等离子体共振能量的Fullerenes/Endofullerenes的PS形成研究中可以汲取的科学将介绍PS光谱的新方向，产卵实验。该奖项反映了NSF的法定任务，并通过使用该基金会的智力功能和广泛的影响来评估NSF的法定任务，并被认为是诚实的支持。

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