Spin Dynamics of Photogenerated Multi-Spin Systems

本课题由化学系化学结构、动力学机制B项目资助，由Michael R.西北大学化学系的Wasielewski正在开发具有可控自旋传输特性的新分子。这些分子以新的信息处理策略为目标，并利用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的广泛应用。使用有机材料和生物启发的方法来实现这一目标提供了开发新结构的可能性，这些结构不仅是通用的，而且是成本效益和环境友好的。 该集团通过与西北大学STEM教育合作伙伴关系办公室（OSEP）的合作关系，与当地的初中和高中保持着持续的关系。他们与OSEP合作，正在开发对教学有用的教材，并将研究纳入学习和教育。此外，还定期举办为期1-2天的专业发展研讨会，并为教师提供为期一周的工作阴影体验，以提供将学生与西北大学丰富的学习资源联系起来的乘数效应。具有特定供体-受体距离和取向的共价连接的有机供体-受体分子内的快速光引发电子转移导致形成具有明确定义的初始自旋构型和磁相互作用的自旋相关自由基对（SCRPs）。时间分辨电子顺磁共振（EPR）和脉冲EPR光谱被用来操纵，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点的自旋共享如何影响SCRPs中的相干退相;电子从光激发的稳定自由基转移到远处的位点如何影响自旋相干性;相干自旋状态如何使用SCRPs在长的分子内距离上传播;以及光生SCRP如何在三重对称分子系统中产生瞬态自旋挫折并传播自旋相干性。 该项目位于有机，物理和材料化学的界面，因此非常适合各级科学家的教育。 该小组也有能力为科学领域代表性不足的学生提供最高水平的教育和培训。涉及K-12学生及其教师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.