Anharmonic RRKM calculation for the dissociation of (H(2)O)(2)H(+) and its deuterated species (D(2)O)(2)D(+).
Anharmonic RRKM calculation for the dissociation of (H(2)O)(2)H(+) and its deuterated species (D(2)O)(2)D(+).
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DOI：
10.1021/jp103782r
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发表时间：
2010-09
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
本文报道了水合质子离子（H(2)O）(2)H（+）及其氘化态（D(2)O）（2)D(+)）的解离动力学，采用过渡态理论和从头计算，基于谐振子和非谐振子模型。我们发现，由于活化能的存在，（H(2)O）(2)H（+）和（D(2)O）(2)D（+）的解离表现出明显的阈值行为。此外，在高能或高温范围内，调和与非调和解离速率常数之间的偏差变得更大，在谐振子模型下，速率常数变得不合理地大。发现同位素效应变得更加明显，但仅在非谐振子模型的情况下。这些结果表明，非调和Rice-Ramsperger-Kassel-Marcus （RRKM）理论可以很好地描述（H(2)O）(2)H（+）和（D(2)O）(2)D（+）的解离。以（H(2)O）(2)H（+）和（D(2)O）(2)D（+）为例，从RRKM理论的角度建立了振动预解离光谱（VPS）原理的理论模型，并应用于确定实验条件和理解解离速率常数k(E)在VPS实验中的作用。
Investigations on the dissociation kinetics of hydrated protonium ions, (H(2)O)(2)H(+) and their deuterated species (D(2)O)(2)D(+), are reported based on the harmonic and anharmonic oscillator model using the transition state theory and ab initio calculations. We find that the dissociation of (H(2)O)(2)H(+) and (D(2)O)(2)D(+) exhibits a distinct threshold behavior due to the existence of activation energies. Moreover, the deviation between the harmonic and anharmonic dissociation rate constants becomes larger in the high energy or temperature range, with the rate constants becoming unreasonably large under the harmonic oscillator model. The isotope effect is found to become more distinct but only in the case of the anharmonic oscillator model. These results show that the anharmonic Rice-Ramsperger-Kassel-Marcus (RRKM) theory can provide a reasonably good description for the dissociation of (H(2)O)(2)H(+) and (D(2)O)(2)D(+). Furthermore, a theoretical model to demonstrate the principle of vibrational predissociation spectroscopy (VPS) is established from the viewpoint of RRKM theory and applied in determining the experimental conditions and understanding the role of the dissociation rate constant k(E) played in the VPS experiment, using (H(2)O)(2)H(+) and (D(2)O)(2)D(+) as examples.