The spin-forbidden reaction CH „ 2 P ... 1 N 2 ̃ HCN 1 N „ 4 S ... revisited . II . Nonadiabatic transition state theory and application
The spin-forbidden reaction CH „ 2 P ... 1 N 2 ̃ HCN 1 N „ 4 S ... revisited . II . Nonadiabatic transition state theory and application
复制标题
自旋禁阻反应CH``2P...1N2̃HCN1N``4S...重温非绝热过渡态理论与应用。
DOI：
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发表时间：
1999
期刊：
影响因子：
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通讯作者：
S. Klippenstein
中科院分区：
文献类型：
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作者：
Q. Cui;K. Morokuma;J. Bowman;S. Klippenstein
本文将过渡态理论直接推广到非绝热过程，并应用于研究自旋禁戒反应CH ~P！1N2→ HCN 1N（S）。采用扭曲波近似和自旋轨道耦合的从头算方法，建立了一维模型，计算了系统间的交叉几率。然后通过能量卷积与振动频率考虑正交自由度的影响，从从头计算获得，正交于交叉缝的最小交叉缝~MSX！，也从从头计算得到。通过对统一统计理论的直接扩展，得到了反应的累积反应概率N（E）的表达式，其中MSX被视为过渡态。计算的热速率常数，k（T），似乎是太低了两个数量级相比，实验测量和经验过渡态的研究，其中经验振动频率在MSX是由一个因子2比这里推导出的。这种分歧强烈表明，目前对多层面动态的处理需要改进。特别地，在我们考虑的情况下，自旋禁戒跃迁以均匀概率在接缝上发生的假设可能是不好的。© 1999年美国物理研究所。@S0021-9606 ~99！02419-8#
Transition state theory is extended straightforwardly to treat nonadiabatic processes and applied to study the rate constant of the spin-forbidden reaction CH ~P!1N2→HCN1N(S). A one-dimensional model was set up to calculate the intersystem crossing probability with the distorted wave approximation and using an ab initio value of the spin–orbit coupling. The effect of orthogonal degrees of freedom was then considered by energy convolution with the vibrational frequencies, obtained fromab initio calculations, orthogonal to the crossing seam at the minimum of the seam of crossing ~MSX!, also obtained fromab initio calculations. An expression for the cumulative reaction probability, N(E), of the reaction was obtained by a straightforward extension of the unified statistical theory, where the MSX was treated as a transition state. The calculated thermal rate constant, k(T), seems to be too low by two orders of magnitude compared to experimental measurements and an empirical transition state study where empirical vibrational frequencies at the MSX are lower by a factor of 2 than those derived here. The disagreement strongly suggests that the current treatment of the multidimensional dynamics needs to be improved. In particular, it may be a poor assumption that spin-forbidden transition takes place with uniform probability on the seam in the case we are considering. © 1999 American Institute of Physics. @S0021-9606 ~99!02419-8#