Experimental and theoretical studies of the O(3P) + C2H4 reaction dynamics: collision energy dependence of branching ratios and extent of intersystem crossing.
Experimental and theoretical studies of the O(3P) + C2H4 reaction dynamics: collision energy dependence of branching ratios and extent of intersystem crossing.
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DOI：
10.1063/1.4746758
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发表时间：
2012-08
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影响因子：
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通讯作者：
Bina Fu;Yong‐Chang Han;J. Bowman;F. Leonori;N. Balucani;L. Angelucci;A. Occhiogrosso;R. Petrucci;P. Casavecchia
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文献类型：
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作者：
Bina Fu;Yong‐Chang Han;J. Bowman;F. Leonori;N. Balucani;L. Angelucci;A. Occhiogrosso;R. Petrucci;P. Casavecchia
O((3)P)与C(2)H(4)的反应在燃烧和大气化学中具有重要意义，它不仅包括指示的三重态势能面(PES)，而且还包括耦合到三重态表面的交错单态势能面(PES)。由于这些势的坚固性和高维性，以及碰撞络合物的长寿命，这种反应给理论和实验带来了巨大的挑战。用软电子电离探测的交叉分子束(CMB)散射实验对碰撞能E(C)为8.4kcal/mol的多原子多通道反应动力学进行了解缠。确定并表征了五种不同的初级产物，它们分别对应于H+CH(2)CHO、H+CH(3)CO、CH(3)+HCO、CH(2)+H(2)CO和H(2)+CH(2)CO的五个放热竞争通道。这些实验扩展了我们以前在较高碰撞能(E(C)∼13kcal/∼)下所做的工作，并将结果与文献中的室温动力学实验支化比(E(C)mg1kcal/mo1)相结合，可以探索在较大碰撞能量范围内支化比的变化。用从头算方法对O((3)P)+C(2)H(4)反应的单重态和三重态及其耦合进行了全维QCT表面跃迁计算，计算的能量分别对应于CMB和动力学能.理论和实验都发现，从产物通道分支比和系间交叉程度(ISC)的碰撞能量依赖关系来看，三重态表面和单重态表面对反应的贡献几乎相等。对H+CH(2)CHO、CH(3)+HCO和CH(2)+H(2)CO三种初级自由基通道产物的角分布和平动能分布进行了详细的理论和实验比较。理论和实验的良好一致性表明，QCT表面跃迁计算，使用可靠的耦合多维PESS，可以得到准确的多原子多通道反应的动力学信息，而ISC在其中起着重要的作用。
The reaction of O((3)P) with C(2)H(4), of importance in combustion and atmospheric chemistry, stands out as paradigm reaction involving not only the indicated triplet state potential energy surface (PES) but also an interleaved singlet PES that is coupled to the triplet surface. This reaction poses great challenges for theory and experiment, owing to the ruggedness and high dimensionality of these potentials, as well as the long lifetimes of the collision complexes. Crossed molecular beam (CMB) scattering experiments with soft electron ionization detection are used to disentangle the dynamics of this polyatomic multichannel reaction at a collision energy E(c) of 8.4 kcal∕mol. Five different primary products have been identified and characterized, which correspond to the five exothermic competing channels leading to H + CH(2)CHO, H + CH(3)CO, CH(3) + HCO, CH(2) + H(2)CO, and H(2) + CH(2)CO. These experiments extend our previous CMB work at higher collision energy (E(c) ∼ 13 kcal∕mol) and when the results are combined with the literature branching ratios from kinetics experiments at room temperature (E(c) ∼ 1 kcal∕mol), permit to explore the variation of the branching ratios over a wide range of collision energies. In a synergistic fashion, full-dimensional, QCT surface hopping calculations of the O((3)P) + C(2)H(4) reaction using ab initio PESs for the singlet and triplet states and their coupling, are reported at collision energies corresponding to the CMB and the kinetics ones. Both theory and experiment find almost an equal contribution from the triplet and singlet surfaces to the reaction, as seen from the collision energy dependence of branching ratios of product channels and extent of intersystem crossing (ISC). Further detailed comparisons at the level of angular distributions and translational energy distributions are made between theory and experiment for the three primary radical channel products, H + CH(2)CHO, CH(3) + HCO, and CH(2) + H(2)CO. The very good agreement between theory and experiment indicates that QCT surface-hopping calculations, using reliable coupled multidimensional PESs, can yield accurate dynamical information for polyatomic multichannel reactions in which ISC plays an important role.