Roaming反应通道的激发态动力学研究

项目名称： Roaming反应通道的激发态动力学研究

项目编号： No.21203242

项目类型： 青年科学基金项目

立项/批准年度： 2013

项目学科： 物理化学

项目作者： 华林强

作者单位： 中国科学院武汉物理与数学研究所

项目金额： 28万元

中文摘要： 过渡态理论是化学反应动力学最基本的理论之一,它能够预言反应的速率、机理等。然而2004年，过渡态理论的例外- - "徘徊"(roaming)反应机理的发现，激发了人们对该理论不足之处的思考。最近(2012年)，人们首次发现激发态上也存在roaming反应通道，这一重大发现深化了我们对roaming反应机理的认识。然而，激发态上roaming 的反应速率是多少这一直观问题并没有得到解答。鉴于此，我们提出采用时间分辨的质谱结合时间分辨的切影像技术，通过测量不同反应通道生成产物的时间来测量反应的速率。我们将研究NO3和硝基苯解离时roaming生成NO这两个代表性反应,并直接回答NO3激发态(和基态)上roaming的反应速率问题；而对于硝基苯，我们将得到基态和未知通道上生成NO的速率并探讨未知通道来自激发态的可能性。本研究不仅为新的化学反应理论提供可靠的参数，还将启发我们对激发态动学展开新的思考。

中文关键词： 飞秒脉冲；时间分辨；“漫游”机理；激发态动力学；

英文摘要： The transition state theory has been central to chemistry because the products, rates, and dynamics of a reaction are often determined by the "transition state" (TS) configuration. In 2004, however, a non-TS mechanism, named as "roaming mechanism", in which the reaction products and kinetics that cannot be predicted by current TS theories, was reported and challenged our current understanding of reaction rate theories. Up to now, it is generally believed that roaming occurs on the ground state potential energy surface (PES). Interestingly, a novel roaming mechanism, which evolves along the excited-state PES, has been found for the first time in the photodissociation of NO3 (Science, Vol. 335, page 1075, 2012). This discovery marks a significant advance in the study of roaming dynamics and, at the same time, poses many open questions on this excited-state roaming mechanism. One of them,for example, is how fast the roaming is on the excited state PES? Since it can not be predicted by current TS theories, it is necessary to provide trustable experimental data. In this proposal, roaming pathways in dissociation of NO3 and C6H5NO2 will be studied using time-resolved mass spectra in combination with time-resolved slice image technique. With our method, one can distinguish the reaction pathways by the size of the image

英文关键词： femtosecond laser；time-resolved spectroscopy；roaming mechanism；excited state dynamics；