苯酚态-态光解动力学的理论研究

The photodissociation process of molecules is one of the key issues in chemistry and its dynamics and the species involved in this process play important roles in stimulating atmospheric chemistry, interstellar chemistry, combustion chemistry, and environmental chemistry. Although the modern laser techniques are mature in the application and investigation of spectroscopy, the quantum photodissociation study at the state-to-state level is scarce. The photodissociation process of phenol system includes many degrees of freedom and is at high total energy and includes lots of open product states, which make the study of the state-to-state photodissociation dynamics more challenging. In this proposal, based on the first principles, we will construct highly accurate ground and excited potential energy surfaces including non-adiabatic couplings for the phenol molecule. We will construct the efficient four-dimensional and more accurate six-dimensional theoretical computation models, and study the state-to-state photodissociation dynamics. Further, with close combination of experimental studies, we will reveal the nature of the photodissociation of the related polyatomic molecules, and provide a theoretical platform for the further related gas-phase reaction model and experimental studies. The proposed research will greatly improve our understandings of detailed microscopic mechanism of photodissociation and play important roles in the achievement of controlling the photodissociation process and the protection of human living environment.

分子光解过程是化学中的核心问题之一, 其动力学特性和解离过程中涉及的分子物种在模拟大气化学、星际化学、燃烧化学和环境化学等方面具有重要的作用。虽然现代激光技术在光谱方面的应用和研究都已经比较成熟，但在态-态水平上的光解量子动力学研究尚不多。苯酚分子体系的光解过程由于涉及较多的自由度，并且总能量较高，有许多开放的产物态，这也给态-态光解动力学研究带来了困难。本项目拟从第一性原理出发，构建苯酚的高精度基态和激发态势能面及其非绝热耦合；建立有效的4维和更加精确的6维动力学计算模型，并研究其态-态光解动力学性质，与实验结果紧密结合，揭示相关多原子分子的光解本质，为进一步的相关气相反应模型和实验研究提供理论依据。本项目的研究对深入理解和认识一些重要多原子分子的微观光解机制,实现对光解过程的激光调控和人类生存环境的保护等都具有重要意义。

本项目主要开展了多原子分子苯酚（以及苯硫酚）的非绝热态-态光解动力学的理论研究，取得了重要进展。发展了处理带苯环分子动力学的减维模型，基于4态的非绝热模型，利用实波包方法首次在量子水平下计算得到了苯酚及氘代苯酚分子S1态的不同振动能级态的寿命，且与实验值一致；理论预测的同位素效应也和实验结果吻合；并发现常用的Born-Oppenheimer绝热模型不能正确描述锥形交叉处的动力学过程，因其没有包含几何相因子，计算结果表明几何相效应在苯酚S1态的非绝热隧穿过程中起着重要作用。采用高级别量子化学从头算方法，利用“线性振电耦合”模型，发展了减维（3维）苯硫酚电子基态（S0态）和第一、第二电子激发态（S1和S2态）的非绝热势能面，计算了苯硫酚及氘代苯硫酚的S0和非绝热耦合的S1态的2维和3维振动能级，与实验结果吻合；新构建的非绝热势能面为进一步的光解动力学的理论研究提供了重要可靠基础；另外，研究了振动介导的NH3分子光解动力学，结合实验结果，阐明了氨分子的光解动力学中的模式特异性机制。在国际重要学术期刊上发表论文7篇，其中2篇JACS, 2篇JCP, 1篇JPCL。培养了一名博士。