Unraveling unconventional photochemistry using time- and state-resolved imaging

在这个由化学部化学结构和动力学计划A资助的项目中，加州大学欧文分校的克雷格默里博士和他的研究生们正在使用短和超短激光脉冲来探索小分子与光的相互作用。在吸收足够高能量的光后，这些小分子通过不同的途径和不同的时间尺度解离。这些过程的详细信息是通过产品的时间分辨成像获得的。 一个推广计划涉及积极参与当地高中教师的研究实验室，为他们提供一些当前的研究活动的见解。 该计划还为学生提供了一天的大学体验，让他们接触到高等教育的机会。 该计划绘制在实验室和更大规模的应用研究的基本化学过程之间的连接。 该项目使用速度图（切片）离子成像耦合到可调谐纳秒和皮秒激光系统来测量相关的光碎片产物状态分布。利用该技术，探索了气相小分子中的非常规光化学过程，如漫游介导的系间交叉，多个漫游路径和原子或自由基物种的挤出。 使用变换限制皮秒脉冲的时间分辨测量探索相关产物状态分布如何随时间演变，识别漫游，系统间交叉和常规解离机制的特征时间尺度。

In this project funded by the Chemical Structure and Dynamics Program A of the Chemistry Division, Dr. Craig Murray of University of California, Irvine and his graduate students are using short and ultrashort laser pulses to explore interactions of small molecules with light. After absorbing light of sufficiently high energy, these small molecules dissociate via different pathways and with different time scales. Detailed information on these processes is obtained by time-resolved imaging of the products. An outreach program involves active participation in the research lab of local high school teachers, providing them with insight into some current research activity. The program additionally provides a day at university experience for their students, exposing them to opportunities available to them in higher education. The program draws connections between fundamental chemical processes studied in the laboratory and larger scale applications. This project uses velocity-map (slice) ion imaging coupled to tunable nanosecond and picosecond laser systems to measure correlated photofragment product state distributions. With this technique, unconventional photochemical processes in small gas-phase molecules are explored, such as roaming-mediated intersystem crossing, multiple roaming pathways and extrusion of atomic or radical species. Time-resolved measurements using transform-limited picosecond pulses explore how the correlated product state distributions evolve in time, identifying characteristic time-scales for roaming, intersystem crossing, and conventional dissociation mechanisms.