Ultrafast time-resolved studies of reactive intermediates

技术概述：该项目将使用超快时间分辨紫外-可见和红外光谱来研究光激发前驱体中碳烯和异构烯烃的诞生。该研究小组将通过监测C=C和C=O波段（如果可用），或使用时间分辨红外光谱监测750至1000厘米（-1）之间的面外弯曲区域，研究极性和非极性烯烃形成。该项目的主要目标是产生有关以下方面的独特数据：(a)重氮和重氮激发态内部转化和破碎之间的竞争；(b)了解振动激发、开壳、单线态碳烯的化学性质；(c)全松弛闭壳单重态碳烯的动力学。这项研究将揭示重氮或重氮化合物在吸收光后的最初0.3 - 2000 ps期间化学转化的动力学和机理途径。第二个目标是利用超快时间分辨红外光谱研究振动松弛烷基取代闭壳单重态碳烯异构化的动力学。1,2-氢移位反应具有基本的基础意义，这些努力将系统地改变碳烯和溶剂的结构，从而首次对这一经典反应进行广泛和定量的描述。非技术总结：这项工作将提高光化学的理解水平和可预测性，使其更接近基态化学的成熟水平。这些努力将促进计算工具的发展，这些工具可以定量地预测光化学和光物理过程。该项目将产生的数据将帮助理论家开发具有足够预测能力的方法，以帮助设计光化学反应。这些计算和实验研究将协同工作，训练和教育学生关于反应性中间体和研究它们的方法。有价值的新数据将可用于评估这些不寻常的反应中间体的固有特性和反应性，并且已经存在工业应用，特别是在光刻和半导体制造中。研究生将接受实验和理论研究方面的培训，而团队也将通过研究活动以及教育外展和参与接触到K-16社区。

TECHNICAL SUMMARY:This project will use ultrafast time-resolved UV-vis and IR spectroscopy to study the birth of carbenes and isomeric alkenes from photo-excited precursors. This research team will study both polar and non-polar alkene formation by monitoring the intense C=C and C=O bands, if available, or the out-of-plane bending region between 750 and 1000 cm(-1) using time-resolved IR spectroscopy. The primary goal of the project is to generate unique data concerning: (a) the competition between internal conversion and fragmentation in diazo and diazirine excited states; (b) to understand the chemistry of vibrationally excited, open-shell, singlet carbenes; and (c) the dynamics of fully relaxed closed-shell singlet carbenes. This study will reveal the dynamics and mechanistic pathways of chemical transformations that proceed during the first 0.3 - 2000 ps after a diazirine or diazo compound absorbs light. The secondary goal is to study the dynamics of isomerization of vibrationally relaxed alkyl substituted closed-shell singlet carbenes to alkenes using ultrafast time-resolved IR spectroscopy. The 1,2-hydrogen shift reaction is of basic fundamental interest, and these efforts will systematically vary the structure of carbenes and solvent to provide the first broad and quantitative description of this classic reaction.NON-TECHNICAL SUMMARY:This work will raise the level of understanding and predictability of photochemistry and bring it closer to the level of maturity of ground state chemistry. These efforts will spur the development of computational tools that can quantitatively predict photochemical and photophysical processes. The project will generate data that will help theorists develop methods with sufficient predictive power to aid the design of photochemical reactions. These computational and experimental investigations will work synergistically to train and educate students about reactive intermediates and the means to study them. Valuable new data will be available to evaluate the intrinsic properties and reactivity of these unusual reactive intermediates, and for which industrial applications already exist, particularly in lithography and semiconductor manufacturing. Graduate students will be trained in conducting research, both experimentally and theoretically, while the team will also reach out to the K-16 communities with research activities as well as educational outreach and engagement.