Towards State-to-State Photodissociation Dynamics of Polyatomic Free Radicals: Probing Nonadiabatic Processes and Competitive Pathways

加州大学河滨分校张劲松教授在化学学部化学结构、动力学和机理项目资助下，研究了多原子自由基的光解动力学。自由基是许多化学反应环境中重要的反应中间体。从这项工作中获得的基础知识（光谱学、能量学、反应机理等）对燃烧、大气化学、有机化学以及理论化学和物理学界都是有价值的。这项工作的更广泛影响还包括推进研究生的教育和培训，促进女性和加州大学河滨分校未被充分代表的少数族裔的本科研究经验。该项目还包括向河滨和圣贝纳迪诺社区学院的多元化学生群体提供服务。本研究的目的是在量子精度上提供对原型多原子自由基的光化学反应性及其非绝热动力学和竞争途径的定量理解。该项目侧重于几个基准体系，如甲基、乙基和HCO自由基。采用高分辨率、高灵敏度、高n里德伯原子飞行时间（HRTOF）技术作为主要实验工具，对这些体系的h原子光产物进行了表征。该技术提供状态解析的，甚至状态到状态的乘积能量和角分布。这些实验旨在提供高质量的数据和基准，以测试受激开壳种的高水平量子力学理论。

In this project funded by the Chemical Structure, Dynamics and Mechanisms program of the Chemistry Division, Professor Jingsong Zhang of the University of California at Riverside investigates the photodissociation dynamics of polyatomic free radicals. Free radicals are important reactive intermediates in many reactive chemical environments. The fundamental knowledge (spectroscopy, energetics, reaction mechanisms, etc.) from this work is valuable to the combustion, atmospheric chemistry, and organic chemistry communities, as well as the theoretical chemistry and physics communities. The broader impacts of this work also include advancing education and training of graduate students, promoting undergraduate research experience of women and underrepresented minority at the University of California at Riverside. The project also includes outreach to a diversified student population of the Riverside and San Bernardino community colleges.The goal of this research is to provide quantitative understanding of the photo-chemical reactivity of prototypical polyatomic radicals and their nonadiabatic dynamics and competitive pathways at quantum accuracy. The project focuses on several benchmark systems, such as the methyl, ethynyl, and HCO radicals. The H-atom photoproducts of these systems are characterized using the high-resolution, high-sensitivity high-n Rydberg atom time-of-flight (HRTOF) technique as the main experimental tool. This technique provides state-resolved or even state-to-state product energy and angular distributions. These experiments aim to render high-quality data and benchmarks to test high-level quantum mechanical theories of the excited open-shell species.