Spin Dynamics of Photogenerated Multi-Spin Systems

在这个由化学系化学结构、动力学和机制B计划资助的项目中，西北大学化学系的Michael R.Wasielewski教授正在开发具有可控自旋传输特性的新分子。这些分子瞄准了新的信息处理策略，并利用了电子自旋的量子性质。这项工作可能会导致先进的计算机技术在整个社会得到广泛的应用。使用有机材料和生物启发的方法来实现这一目标，为开发不仅具有多种用途，而且具有成本效益和环境友好的新结构提供了可能性。该组织通过与西北大学STEM教育伙伴关系办公室(OSEP)建立合作伙伴关系，与当地初中和高中保持着持续的关系。与OSEP合作，他们正在开发在教学中有用的教育材料，并将研究纳入学习和教育。此外，定期举办1-2天的专业发展研讨会，并为教师实施为期一周的职业跟踪体验，以提供倍增效应，将学生与西北大学丰富的学习资源联系起来。在具有特定给体-受体距离和取向的共价连接的有机给体-受体分子中，光引发的快速电子转移导致具有明确的初始自旋构型和磁性相互作用的自旋相关自由基对(SCRP)的形成。时间分辨电子顺磁共振(EPR)和脉冲EPR谱被用来操纵、控制和观察这些相干自旋态。这项新的研究调查了多个自由基位置上的自旋共享如何影响SCRP中的相干消相；电子从光激发的稳定自由基到远程位置的电子转移如何影响自旋相干性；相干自旋态如何使用SCRP在分子内长距离传播；以及光生SCRP如何在三重对称分子系统中产生瞬时自旋受挫和传播自旋相干性。该项目位于有机化学、物理化学和材料化学的交界处，因此非常适合各级科学家的教育。这一群体也处于有利地位，可以为科学方面代表性不足的学生提供最高水平的教育和培训。K-12学生及其教师参加的外联活动是该项目的一部分。

In this project, funded by the Chemical Structure, Dynamics & Mechanisms B Program of the Chemistry Division, Professor Michael R. Wasielewski of the Department of Chemistry at Northwestern University is developing new molecules with controllable spin transport properties. These molecules target new information processing strategies and take advantage of the quantum nature of electron spin. This work may lead to advanced computer technologies with broad applications throughout society. The use of organic materials and bio-inspired approaches to achieve this goal offers the possibility of developing new structures that are not only versatile, but are cost effective and environmentally benign as well. The group has an ongoing relationship with local middle and high schools through a partnership with the Office of STEM Education Partnership (OSEP) at Northwestern University. Working with OSEP, they are developing educational materials useful in teaching and for incorporating research into learning and education. Additionally, regular 1-2 day professional development workshops are held and week-long job shadowing experiences for teachers are implemented to provide a multiplier effect in connecting students to the rich learning resources at Northwestern University. Fast photo-initiated electron transfer within covalently-linked organic donor-acceptor molecules having specific donor-acceptor distances and orientations results in the formation of spin-correlated radical pairs (SCRPs) having well-defined initial spin configurations and magnetic interactions. Time-resolved electron paramagnetic resonance (EPR) and pulse-EPR spectroscopy are used to manipulate, control, and observe these coherent spin states. This new research investigates how spin sharing over multiple radical sites influences coherence dephasing in SCRPs; how electron transfer from a photo-excited stable radical to a distant site affects spin coherence; how coherent spin states can be propagated over long intramolecular distances using SCRPs; and how a photo-generated SCRP can produce transient spin frustration and propagate spin coherence within a three-fold symmetric molecular system. The project lies at the interface of organic, physical, and materials chemistry, and is therefore well suited to the education of scientists at all levels. This group is also well-positioned to provide the highest level of education and training for students underrepresented in science. Outreach activities involving K-12 students and their teachers are part of the project.