Paul Amit K, Kolakkandy Sujitha, Hase William L
Department of Chemistry and Biochemistry Texas Tech University, Lubbock, Texas 79409, United States.
J Phys Chem A. 2015 Jul 16;119(28):7894-904. doi: 10.1021/acs.jpca.5b01922. Epub 2015 May 18.
Chemical dynamics simulations were used to study Bz + Na(+)(Bz) → Na(+)(Bz)2* association and the ensuing dissociation of the Na(+)(Bz)2* cluster (Bz = benzene). An interesting and unexpected reaction found from the simulations is direct displacement, for which the colliding Bz molecule displaces the Bz molecule attached to Na(+), forming Na(+)(Bz). The rate constant for Bz + Na(+)(Bz) association was calculated at 750 and 1000 K, and found to decrease with increase in temperature. By contrast, the direct displacement rate constant increases with temperature. The cross section and rate constant for direct displacement are approximately an order of magnitude lower than those for association. The Na(+)(Bz)2* cluster, formed by association, dissociates with a biexponential probability, with the rate constant for the short-time component approximately an order of magnitude larger than that for the longer time component. The latter rate constant agrees with that of Rice-Ramsperger-Kassel-Marcus (RRKM) theory, consistent with rapid intramolecular vibrational energy redistribution (IVR) and intrinsic RRKM dynamics for the Na(+)(Bz)2* cluster. A coupled phase space model was used to analyze the biexponential dissociation probability.
采用化学动力学模拟研究了Bz + Na⁺(Bz) → Na⁺(Bz)₂缔合反应以及随后Na⁺(Bz)₂团簇（Bz = 苯）的解离。模拟中发现的一个有趣且意想不到的反应是直接取代反应，即碰撞的Bz分子取代附着在Na⁺上的Bz分子，形成Na⁺(Bz)。计算了750 K和1000 K时Bz + Na⁺(Bz)缔合反应的速率常数，发现其随温度升高而降低。相比之下，直接取代反应的速率常数随温度升高而增大。直接取代反应的截面和速率常数比缔合反应的大约低一个数量级。通过缔合形成的Na⁺(Bz)₂团簇以双指数概率解离，短时间分量的速率常数比长时间分量的大约大一个数量级。后者的速率常数与赖斯 - 拉姆施佩格 - 卡塞尔 - 马库斯（RRKM）理论的速率常数一致，这与Na⁺(Bz)₂团簇内快速的分子内振动能量重新分布（IVR）和RRKM本征动力学相符。使用耦合相空间模型分析双指数解离概率。
