MEASUREMENTS OF STATE-RESOLVED DIFFERENTIAL CROSS SECTIONS VIA HIGH-RESOLUTION POLARIZED DOPPLER SPECTROSCOPY

用多普勒分辨偏振光谱研究了基元气相反应的化学反应动力学。利用这种技术，可以用状态分辨的方式测量微分截面。用高分辨染料激光激发无碰撞双原子产物分子，分析其多普勒展宽谱线，提取微分截面和转动角动量极化等矢量性质的信息，我们研究了O（^1D）原子与几种简单分子的反应。显示了以下结果。1)对于H_2反应，反应几率的微分截面和碰撞能依赖性强烈地依赖于产物OH分子的振转态。在最近最先进的ab init上与准经典轨道计算的临界比较 ...更多信息 IO势能面2)对于N_2O反应，尽管没有深势阱，但由于反应中间体在所有自由度范围内的有效能量随机化，产物NO分子的振转态分布呈现明显的统计分布。这种行为通常被解释为分子间振动能量的重新分配，重点是轻（氢）原子效应。3)对于C_2H_4和C_2H_6反应，插入O原子形成醇型中间体后反应中间体结构变化的差异反映在产物OH分子转动角动量极化的差异上。4)对于H_2O反应，主要反应途径是O原子插入H_2O的HO键，生成HOGH作为中间体，这一结果只有用态分辨偏振多普勒光谱才能得到。此外，本研究的一些发现给出了新的理解，这与以前基于不充分的状态分辨测量的理解相反。以这种方式阐明基本双分子反应的研究对于化学反应动力学的基本理解是必不可少的。少

Chemical reaction dynamics of elementary gas phase reactions have been studied via Dopplerresolved polarization spectroscopy. By using this technique, differential cross sections can be measured state-resolved manner. Furthermore, this method enables us to measure the polarization of the rotational angular momentum of reaction products.Collision-free diatomic product molecules were probed with high-resolution dye laser excitation and its Doppler-broadened line profiles were analyzed to extract the information of vector properties such as differential cross sections and rotational angular momentum polarization, We investigated the reaction of O(^1D) atom with some several simple molecules. Following results are shown. 1) For H_2 reaction, differential cross sections and collision energy dependence of reaction probability strongly depend on ro-vibrational states of product OH molecules. Critical comparison with a quasi-classical trajectory calculation on a recent state-of-the-art ab init … More io potential energy surfaces. 2) For N_2O reaction, efficient energy randomization within all the degrees of freedom of reaction intermediates leads apparent statistical ro-vibrational state distribution of product NO molecules despite the absence of a deep potential well. Such a behavior is generally interpreted in terms of intermolecular vibrational-energy redistribution, with the emphasis of the light (hydrogen) atom effect. 3) For C_2H_4 and C_2H_6 reaction, the difference of the structural change of reactive intermediates after the insertion of 0 atom forming alcohol type intermediates is reflected in the difference of the polarization of rotational angular momentum of product OH molecules. 4) For H_2O reaction, the main reaction path is an insertion of O atom into HO bond of H_2O forming HOGH as an intermediate.To obtain such findings becomes possible only by the use of the state-resolved polarized Doppler spectroscopy. In addition, some of the findings in this study give new understandings which are opposite to the previous ones based on insufficient state-resolved measurements. The study elucidating elementary bimolecular reactions in this manner is essential for the fundamental understanding of chemical reaction dynamics. Less