基于量子实波包方法研究微波催化中的非热效应

Nowadays, microwave heating has been widely used to accelerate chemical reactions in order to increase the reaction rates. However, the microwave chemistry based on the traditional concept of microwave heating and on the use of commercial microwave ovens is being more and more challenged. First, under the same temprature conditions, microwave irradiation could increase the reaction rates, which has been proved by a dozen of experiments; Second, microwaves may also inhibit the reactivity under certain conditions; Last but not the least, reaction path could aslo be changed by microwave radiation. Despite the use of microwaves has become a well-established technique in chemistry that has been found numerous applications in the laboratory as well as in industry, understanding the mechanisms through which they influence chemical reactivity remains quite poor. The discussion of this matter has mainly been confined to an as yet unresolved debate over whether microwave catalysis is caused by thermal effect or some other specific effects. So far, this debate has been supported exclusively by experimental efforts whereas theoretical work on this topic remains surprisingly scare. Therefore, we intent to check the possibly existed nonthermal effects in microwave catalysis, i.e. the changes of reactivity are partly due to the rotational excitation of reactants caused by absorbing microwave energy,according to the study of the easiest A + BC reactions using the time-dependent real wavepacket method.

目前，微波被广泛应用于加快化学反应以提高反应速率。然而，建立在传统微波加热概念和使用商用微波炉上的微波化学却受到了越来越严峻的挑战。首先，实验上已经观测到许多化学反应，在同样温度条件的微波辐射下可以提高反应速率；其次，人们在实验中发现微波在一定条件下也能抑制反应的进行；除此之外,微波还能改变反应路径。尽管目前在化学中使用微波已经成为一项比较成熟的技术，并且微波在实验室以及工业生产中有着大量的应用，人们对于微波如何影响化学反应活性机理的了解仍然比较匮乏。 关于微波催化的机制是来源于热效应，还是一些其他特殊效应的争论也一直没有停止过。尽管，目前已有明显的实验支持微波催化的非热效应，然而理论工作关于这个方面的研究却很少。我们拟采用量子实波包方法，通过研究转动激发对于形如A + BC反应活性的影响，来检验微波催化中可能存在的非热效应之一，即反应活性的改变部分是由于反应物吸收微波而转动激发造成的。

目前，实验上观测到许多化学反应，同样温度条件下的微波辐射既可以提高其反应速率，也能抑制反应的进行，除此之外，微波辐射还能改变反应路径。本项目主要采用量子含时波包方法，研究了微波催化可能存在的非热效应之一，转动激发造成了反应活性以及反应路径的改变。本项目主要研究了以下几类典型反应，（一）需要经过能垒翻越过程的反应；（二）会经历长时间复合中间体产生过程的反应；（三）涉及到多个反应通道的反应。在结合准经典轨线的研究后发现，转动激发引起的反应物极化会对产物的定向和取向效应产生强烈影响，并引起产物散射方向以及反应机理的改变。对于特定的反应利用微波调控，理论上既可以提高其反应速率，也可以抑制反应的进行；而对于某些其它类型的反应，原则上微波辐射会抑制反应的进行；对具有多个反应通道的反应，转动激发也会改变其反应路径。