Adiabatic and nonadiabatic dissociation of ethyl radical

被引:28
作者
Hostettler, Jonas M. [1 ]
Bach, Andreas [1 ]
Chen, Peter [1 ]
机构
[1] ETH, Organ Chem Lab, CH-8093 Zurich, Switzerland
关键词
ab initio calculations; atom-molecule reactions; configuration interactions; excited states; free radical reactions; ground states; molecular dynamics method; organic compounds; photodissociation; potential energy surfaces; MR-CI LEVEL; CONICAL INTERSECTIONS; ANALYTIC EVALUATION; MOLECULAR-DYNAMICS; HYDROGEN-ATOMS; COUPLING TERMS; AB-INITIO; PHOTODISSOCIATION; RELAXATION; PHOTOLYSIS;
D O I
10.1063/1.3058588
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
Direct ab initio molecular dynamics using the trajectory surface hopping method with Tully's fewest switches simulates the photodissociation dynamics of ethyl radical, C2H5, following electronic excitation to the A-state. Nonadiabatic dissociation dominates and produces ground state ethylene and fast hydrogen atoms with an anisotropic angular distribution. Surface hopping also generates hot ground state ethyl radicals followed ultimately by unimolecular dissociation to C2H4+H. The calculated excited state lifetime and the product recoil energy distribution obtained from an ensemble of trajectories are consistent with previous experiments and suggest that a strictly nonadiabatic mechanism can account for nonradiative decay. This process is in competition with adiabatic dissociation producing electronically excited state ethylene and H, a dissociation channel that has not yet been experimentally observed. The branching ratio between adiabatic and nonadiabatic dissociation pathways depends sensitively on the quality of the potential energy surfaces. At the multireference configuration interaction with singles and doubles level of theory, 15% of all trajectories dissociate adiabatically.
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页数:9
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