Yang Jing, Li Qian Shu, Zhang Shaowen
Institute for Chemical Physics, Beijing Institute of Technology, Beijing, 100081, People's Republic of China.
Phys Chem Chem Phys. 2007 Jan 28;9(4):466-9. doi: 10.1039/b612045h. Epub 2006 Nov 15.
The HOOO radical plays a crucial role in atmospheric processes involving the OH radical and O(2) molecule. We present an ab initio molecular orbital theory study on the decomposition reaction of the first excited state HOOO((2)A') with respect to OH and O(2). The geometries and harmonic vibrational frequencies of all stationary points are calculated at the CASSCF and MRCI levels of theory in conjunction with the 6-31+G(d,p) basis set. The potential energy profile of the decomposition reaction is studied at the CASSCF/6-31+G(d,p) level of theory, in which the complete valence orbitals and electrons are included in the active space. The energies of the potential energy profile are further refined at the CASPT2 and MRCI levels of the theory. Additionally, we have determined the interesting reaction process: the HOOO((2)A') radical with C(s) symmetry does not dissociate to OH((2)Pi) and O(2)((3)Sigma(-)(g)) directly as this is forbidden by orbital symmetry, but dissociates to OH((2)Pi) and O(2)((3)Sigma(-)(g)) via the change in symmetry from C(s) to C(infinity v) symmetry with a low barrier.
HOOO自由基在涉及OH自由基和O(2)分子的大气过程中起着关键作用。我们提出了一项关于第一激发态HOOO((2)A')相对于OH和O(2)的分解反应的从头算分子轨道理论研究。所有驻点的几何结构和谐波振动频率在CASSCF和MRCI理论水平下结合6-31+G(d,p)基组进行计算。在CASSCF/6-31+G(d,p)理论水平下研究分解反应的势能面，其中活性空间包含完整的价轨道和电子。势能面的能量在CASPT2和MRCI理论水平下进一步细化。此外，我们确定了有趣的反应过程：具有C(s)对称性的HOOO((2)A')自由基不会直接分解为OH((2)Pi)和O(2)((3)Sigma(-)(g))，因为这被轨道对称性所禁止，而是通过从C(s)到C(∞v)对称性的低势垒变化分解为OH((2)Pi)和O(2)((3)Sigma(-)(g))。
