CH键伸缩振动激发对F/Cl+CHD3总反应性影响的动力学研究

The basic idea of dynamics of molecular reaction is to understand the mechanism of chemical reaction at the molecular level and finally to control the reaction happening exactly in the way as the human need. More and more effort has been made to study complex reaction system recently , for example, from three atom reaction to multi-atom reaction, from reaction in fundamental state to the one in excited state. reactions of F/Cl+CHD3(v1=1), as the benchmark work in complex system, have attracted great attention. The deep investigation, no matter in the experiment or in the theoretical calculation, has been done to find out rich dynamical information. The differential cross section of product in the defined state shows effect of CH bond stretching to this particular channel. However, it is still not clear whether CH stretching decreases the reactivity for all channel of F+CHD3 and whether CH vibrational energy in CH bond can promote reaction more than collision energy in the reaction of Cl+CHD3. In this proposal the product molecule and radical will be ionized by single photon from EUV laser source. Compared with resonance enhanced multi-photon ionization (REMPI),it will detect all products in different states at the same time. It is quite helpful to collect dynamic information of the whole reactivity and ratio of different reaction channels, which can not be obtained in the research before. This work will give us the clear answer of two questions above.

在分子层次上理解化学反应机理是分子反应动力学的根本目的。目前，从三原子到多原子，从基态到激发态，从简单体系到复杂体系是分子反应动力学领域的发展趋势。F/Cl+CHD3(v1=1)反应是复杂反应体系的重要代表，蕴含着丰富的动力学信息。该反应的复杂性引起了国际上专家的广泛关注，实验和理论研究发现CH键伸缩振动对某些特定量子态产物通道有着巨大的影响。尽管如此，CH键伸缩振动是否全面抑制了F +CHD3反应；在Cl+CHD3反应中，振动能是否比平动能更有效地促进反应发生，仍旧是该领域科学家关注的焦点问题。本项目利用先进的极紫外高亮度光源实现产物分子及自由基单光子电离探测，将从全局角度研究这两个经典反应，揭示振动激发对整体反应性及不同产物通道的影响。希望通过本项目的工作，能对上述两个问题给出合理的答案，朝着精确控制化学反应的梦想更进一步。

对化学反应的精准控制一直以来都是科学家们的梦想。在分子反应动力学中，这种控制主要体现在对微观化学反应结果的准确预测和合理解释。在项目执行期间，我们按照研究计划，分别对晚期势垒反应Cl+CH4和早期势垒反应F+CH4展开了系统的研究。其中，在Cl+CH4反应的研究中，我们以Cl+CH4→HCl+CH3为模型反应，通过理论与实验相结合的方式，深入研究了多原子反应中的HLH振荡现象。通过采集0.10-0.24eV的微分截面，我们发现在碰撞能Ec=0.15eV时，产物CH3（ν=0）在后向微分截面上有明显的峰，而理论计算的结果则完美的解释了峰的起源—HLH振荡。这是历史上首次四原子以外多原子体系理论计算与实验结果在微分截面水平的高度吻合，也为我们后期通过理论与实验相结合的方法研究CH键伸缩振动激发对晚期势垒反应（Cl+CHD3）总反应性的影响奠定了基础。在F+CH4反应的研究中，我们利用实验室自行研制的单纵模OPO/A激光器成功制备了泛频饱和激发态（ν3=2）的CH4分子束，并在4.3kcal/mol的碰撞能下研究了其与F原子的反应。通过分析红外光开启和关闭时实验信号的变化，我们确定了红外光的激发效率并以此计算出了激发态反应的反应性。结合甲烷分子CH4（ν3=2）局域模的性质，我们成功地解释了不同态产物的表现出的不同反应性，这对Polanyi规则是一种很好的补充和发展，同时研究结果可以与以后单光子探测得到总反应性的结果对照，更加全面的理解振动激发对整体反应性及不同产物通道的影响。