Experimental and theoretical studies of the O(3P)+C2H4 reaction dynamics: Collision energy dependence of branching ratios and extent of intersystem crossing

被引:59
作者
Fu, Bina [1 ,2 ]
Han, Yong-Chang [1 ,2 ]
Bowman, Joel M. [1 ,2 ]
Leonori, Francesca [3 ]
Balucani, Nadia [3 ]
Angelucci, Luca [3 ]
Occhiogrosso, Angela [3 ]
Petrucci, Raffaele [3 ]
Casavecchia, Piergiorgio [3 ]
机构
[1] Emory Univ, Dept Chem, Atlanta, GA 30322 USA
[2] Emory Univ, Cherry L Emerson Ctr Sci Computat, Atlanta, GA 30322 USA
[3] Univ Perugia, Dipartimento Chim, I-06123 Perugia, Italy
关键词
CROSSED MOLECULAR-BEAM; CLASSICAL TRAJECTORY CALCULATIONS; POTENTIAL-ENERGY SURFACES; ATOMIC OXYGEN; REACTIVE SCATTERING; PRODUCT CHANNEL; DYNAMICS; SPECTROSCOPY; ETHYLENE; HYDROGEN;
D O I
10.1063/1.4746758
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The reaction of O(P-3) with C2H4, 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 + CH2CHO, H + CH3CO, CH3 + HCO, CH2 + H2CO, and H-2 + CH2CO. These experiments extend our previous CMB work at higher collision energy (E-c similar to 13 kcal/mol) and when the results are combined with the literature branching ratios from kinetics experiments at room temperature (E-c similar to 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(P-3) + C2H4 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 + CH2CHO, CH3 + HCO, and CH2 + H2CO. 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. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4746758]
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页数:22
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