Anharmonic Rice-Ramsperger-Kassel-Marcus (RRKM) and product branching ratio calculations for the partially deuterated protonated water dimers: dissociation and isomerization.
Anharmonic Rice-Ramsperger-Kassel-Marcus (RRKM) and product branching ratio calculations for the partially deuterated protonated water dimers: dissociation and isomerization.
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DOI：
10.1063/1.4794152
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发表时间：
2013-03
期刊：
影响因子：
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通讯作者：
D. Song;Hongmei Su;F. Kong;Sheng-Hsien Lin
中科院分区：
文献类型：
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作者：
D. Song;Hongmei Su;F. Kong;Sheng-Hsien Lin
部分氘代质子化水二聚体H_2O·H（+）·D_2O、H_2O·D（+）·HDO和HDO·H（+）·HDO是H_3O（+）+D_2O同位素标记反应的重要中间体，它们经历直接解离和间接解离，即在解离之前进行异构化。利用Rice-Ramsperger-Kassel-Marcus理论和从头计算方法，分别计算了它们在谐振子和非谐振子模型下的解离和异构化速率常数。根据解离和异构化速率常数，在各种动力学模型（包括调和和非调和近似）下预测了两种主要产物[HD_2O（+）] scin [H_2DO（+）]的分支比.考虑到实验结果的可行动力学模型表明，在描述解离时包括非谐效应，而异构化采用谐波近似。因此，非谐效应被发现发挥重要作用，影响解离反应，而异构化率被证明是不敏感的非谐或谐振子模型是否被应用。
Partially deuterated protonated water dimers, H2O·H(+)·D2O, H2O·D(+)·HDO, and HDO·H(+)·HDO, as important intermediates of isotopic labeled reaction of H3O(+) + D2O, undergo direct dissociation and indirect dissociation, i.e., isomerization before the dissociation. With Rice-Ramsperger-Kassel-Marcus theory and ab initio calculations, we have computed their dissociation and isomerization rate constants separately under the harmonic and anharmonic oscillator models. On the basis of the dissociation and isomerization rate constants, branching ratios of two primary products, [HD2O(+)]∕[H2DO(+)], are predicted under various kinetics models with the harmonic or anharmonic approximation included. The feasible kinetics model accounting for experimental results is shown to include anharmonic effect in describing dissociation, while adopting harmonic approximation for isomerization. Thus, the anharmonic effect is found to play important roles affecting the dissociation reaction, while isomerization rates are shown to be insensitive to whether the anharmonic or harmonic oscillator model is being applied.