Yonehara Takehiro, Kato Shigeki
Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa, Sakyo-ku, Kyoto 606-8502, Japan.
J Chem Phys. 2006 Aug 28;125(8):084307. doi: 10.1063/1.2338041.
We study quantum dynamics of the multichannel reactions of H(2)CO including the molecular and radical dissociation channels as well as the isomerization ones, H(2)CO-->trans-HCOH and trans-HCOH-->cis-HCOH. For this purpose, the previously developed potential energy function [T. Yonehara and S. Kato, J. Chem. Phys. 117, 11131 (2002)] is refined to give accurate transition state energies and to describe the radical dissociation channel. The cumulative reaction probabilities for the molecular dissociation and two isomerization channels are calculated by using the full Watson Hamiltonian. We also carry out wave packet dynamics calculations starting from the transition state region for the molecular dissociation. A contracted basis set for the angular coordinates is constructed to reduce the size of dynamics calculations. The intramolecular vibrational relaxation dynamics is found to be fast and almost complete within 300 fs. Using the energy filtered wave functions, the time propagation of HCOH population is obtained in the energy range from 81 to 94 kcal/mol. The branching ratio of the radical product is estimated by calculating the time dependent reactive fluxes to the molecular and radical dissociation products.
我们研究了H₂CO多通道反应的量子动力学，包括分子解离通道、自由基解离通道以及异构化通道，即H₂CO→反式-HCOH和顺反异构化trans-HCOH→顺式-HCOH。为此，对先前开发的势能函数[T. Yonehara和S. Kato，《化学物理杂志》117, 11131 (2002)]进行了优化，以给出准确的过渡态能量并描述自由基解离通道。利用完整的沃森哈密顿量计算了分子解离和两个异构化通道的累积反应概率。我们还从分子解离的过渡态区域出发进行了波包动力学计算。构建了角坐标的收缩基组以减小动力学计算的规模。发现分子内振动弛豫动力学很快，在300飞秒内几乎完成。使用能量过滤波函数，在81至94千卡/摩尔的能量范围内获得了HCOH布居的时间演化。通过计算分子和自由基解离产物的时间相关反应通量来估计自由基产物的分支比。
