CAREER: Tabletop Extreme Ultraviolet Spectroscopy of Femtosecond Spin Crossover Dynamics

化学系的化学结构、动力学和机理(CSDM-A)项目获得这一奖项，资助伊利诺伊大学香槟分校(UIUC)的Joshua Vura-Weis教授研究电子自旋态变化的光诱导过程的机制。在某些铁和铁钴络合物吸收可见光后，它们会经历快速的重排(自旋翻转)，并被困在一种可能对实际应用有用的长期状态中。该项目使用的实验技术是桌面极端紫外线(XUV)光谱分析。两个旨在促进本科生深入和持续地参与光谱学研究的讲习班是与UIUC的分子光谱学国际研讨会(ISMS)一起设立的。为期一周的“雪地里的光谱”冬季强化课程为二年级学生提供了物理化学研究所需的基础知识，并允许他们提前一年在国内机构开始高水平的工作。为期两天的本科生ISMS预备会议，类似于为研究生举办的戈登研究研讨会系列，建立了一个年轻研究人员社区，并提高了本科生在主会议上的陈述水平。这种新的光谱方法适用于从光催化到太阳能电池设计的一系列物理化学和无机化学问题。利用飞秒分辨率的极紫外(XUV)瞬时吸收光谱来解析一系列过渡金属配合物的自旋驰豫过程的细节。Vura-Weis小组进一步扩展了其能力，以测量旋转交叉过程中的振动动力学。电子转移和自旋动力学之间的相互作用是开壳过渡金属配合物的光物理和反应活性的关键因素。Vura-Weis团队利用XUV瞬时吸收的自旋态特异性和飞秒时间分辨率来测量铁多吡啶络合物的弛豫级联，特别关注短暂的金属中心三重态的潜在作用。普鲁士蓝光中电子转移和自旋交叉之间的相互作用是在一系列离散的氰基桥接铁钴系统中测量的。在这种情况下，XUV吸收的元素特异性允许独立地探测每种金属的动力学。通过元素特定的XUV脉冲相干振动光谱识别出了门电子动力学的特殊的分子运动。为了让本科生更容易接触到物理化学研究，伊利诺伊大学厄巴纳-香槟分校举办了一个关于光谱学的冬季课程，与国际分子光谱学研讨会(ISMS)有关。此外，在这次会议之前，为期两天的本科生会议发展了一个年轻研究人员的支持性社区。

With this award, the Chemical Structure, Dynamics and Mechanisms (CSDM-A) Program of the Division of Chemistry is funding Professor Joshua Vura-Weis at the University of Illinois at Urbana-Champaign (UIUC) to investigate the mechanism of light-induced processes where the electronic spin state changes. After certain iron and iron-cobalt complexes absorb visible light, they undergo a rapid rearrangement (spin flip) and become trapped in a long-lived state that may be useful for practical applications. The experimental technique used in this project is tabletop extreme ultraviolet (XUV) spectroscopy. Two workshops designed to foster deep and sustained undergraduate engagement in spectroscopy research are established in association with the International Symposium on Molecular Spectroscopy (ISMS) at UIUC. A weeklong "Spectroscopy in the Snow" intensive winter course gives sophomores the foundational knowledge required for physical chemistry research and allows them to begin high-level work in their home institutions one year ahead of schedule. A two-day ISMS pre-conference for undergraduates, analogous to the Gordon Research Seminar series for graduate students, builds a community of young researchers and raises the level of undergraduate presentations at the main conference. The new spectroscopic methods demonstrated in this proposal are applicable for a wide range of problems in physical and inorganic chemistry, from photocatalysis to solar cell design.Extreme ultraviolet (XUV) transient absorption spectroscopy at femtosecond resolution is used to resolve the details of the spin relaxation process in a series of transition metal complexes. The Vura-Weis group further extends its capabilities to measure vibrational dynamics during the spin crossover. The interplay between electron transfer and spin dynamics is a key factor in the photophysics and reactivity of complexes containing open-shell transition metals. The Vura-Weis group uses the spin-state specificity and femtosecond time resolution of XUV transient absorption to measure the relaxation cascade of iron polypyridyl complexes, specifically focusing on the potential role of a short-lived metal-centered triplet state. The interplay between electron transfer and spin crossover in Prussian Blues is being measured in a series of discrete cyano-bridged iron-cobalt systems. In this case, the element specificity of XUV absorption allows the dynamics of each metal to be independently probed. The particular molecular motions that gate the electron dynamics are identified by element-specific XUV impulsive coherent vibrational spectroscopy. To make research in physical chemistry more accessible to undergraduates, a winter school on spectroscopy takes place at the University of Illinois, Urbana-Champaign, in connection with the International Symposium on Molecular Spectroscopy (ISMS). In addition, a two-day undergraduate meeting preceding this conference develops a supportive community of young researchers.