CAREER: Structural and solvent control of nonadiabatic bond formation probed with ultrafast time-resolved spectroscopies

有了这个CAREER奖，化学系的化学结构，动力学和机制（CSDM-A）计划资助约翰霍普金斯大学的亚瑟布拉格教授进行实验研究，研究光驱动的非绝热键形成过程是如何由反应物结构和化学环境控制的。非绝热过程是能量激发分子的基本弛豫途径，并产生快速有效的光化学过程。 目的包括提高对能量转换机制的理解，例如，在光化学和光生物学中，以及确定可以控制光驱动的化学过程的条件。采用多种最先进的研究方法，为学生研究人员提供高水平的培训机会。 这些学生还参与基于网络摄像头的光谱仪和相关的中学化学课程的开发，使化学，光谱学和仪器设计的基本概念的探索。教育目标是通过课程单元和培训教育工作者的专业发展研讨会的发展，与教育推广中心（CEO）在JHU提供的行政计划援助。课程开发的目标是将基本的定量光谱实验整合到课堂项目中，以满足下一代科学标准中概述的新目标。光谱仪和课程材料将提供给巴尔的摩市学校的教师和学生。本研究的目标是确定如何与非绝热电环键的形成和它的整体功效的核动力学的性质从根本上受反应物结构和化学环境。 这项工作特别侧重于邻芳烃和相关系统的光化学动力学，因为这些是易于处理的系统，详细的实验询问。 时间分辨吸收和拉曼光谱用于探测激发分子在低至数十飞秒的时间尺度上的动力学，因为这些是键形成和断裂的时间尺度。 这些测量和支持性量子化学计算的目标是表征分子动力学，所述分子动力学发生在激发时接近和穿过电子状态之间的交叉点，从而引起键形成或其他能量失活途径。 这些系统的光诱导动力学也进行了研究，以探测溶剂-溶质相互作用，影响溶液相化学的过程。 研究结果预计将提供这些过程的结构和溶剂依赖性的实验基准，支持大分子的松弛和能量转移途径的预测经验和计算。

With this CAREER award, the Chemical Structure, Dynamics and Mechanisms (CSDM-A) Program of the Division of Chemistry is funding Professor Arthur Bragg of Johns Hopkins University to conduct experimental investigations on how the course of light-driven nonadiabatic bond formation is controlled by reactant structure and chemical environment. Nonadiabatic processes are fundamental relaxation pathways of energetically excited molecules and give rise to fast and efficient photochemical processes. Aims include improved understanding of energy conversion mechanisms, for example, in photochemistry and photobiology, and determination of conditions under which light-driven chemical processes can be controlled. Multiple state-of-the-art research methods are employed, providing high level training opportunities for student researchers. These students are also involved in development of webcam-based spectrometers and associated secondary-level chemistry curricula, enabling exploration of basic concepts in chemistry, spectroscopy, and instrument design. Educational objectives are met through development of curricular units and professional development workshops for training educators, with administrative program assistance provided by the Center for Educational Outreach (CEO) at JHU. Curriculum development targets integration of basic quantitative spectroscopic experimentation into classroom projects that meet new targets outlined in the Next Generation Science Standards. The spectrometers and curricular materials will be provided to teachers and students in the Baltimore City Schools. The goal of this research is to determine how the nature of nuclear dynamics associated with nonadiabatic electrocyclic bond formation and its overall efficacy are affected fundamentally by reactant structure and chemical environment. The work focuses specifically on the photochemical dynamics of ortho-arenes and related systems, as these are tractable systems for detailed experimental interrogation. Time-resolved absorption and Raman spectroscopies are used to probe dynamics of excited molecules on timescales down to tens of femtoseconds, as these are the timescales on which bonds form and break. These measurements and supportive quantum chemical computations target characterization of molecular dynamics that occur on the approach to and crossing through intersections between electronic states upon excitation, giving rise to bond formation or other energy deactivation pathways. The photoinduced dynamics of these systems is also studied to probe solvent-solute interactions that impact the course of solution-phase chemistry. Findings are expected to provide experimental benchmarks on the structure and solvent dependence of these processes, supporting prediction of relaxation and energy transfer pathways of large molecules both empirically and computationally.