Martínez Rodrigo, González Miguel, Defazio Paolo, Petrongolo Carlo
Departamento de Química, Universidad de La Rioja, C/Madre de Dios 51, 26006 Logroño, Spain.
J Chem Phys. 2007 Sep 14;127(10):104302. doi: 10.1063/1.2762210.
A quantum-mechanical (QM) and quasiclassical trajectory (QCT) study was performed on the title reaction, using a pseudotriatomic ab initio based surface. Probabilities and integral cross sections present some clear peaks versus the collision energy E(col), which we assign to Feshbach resonances of the transition state, where the light H atom oscillates between the heavy Cl and CH(3) groups. For ground-state reactants, reactivity is essentially of quantum origin (QCT observables and oscillations are smaller, or much smaller, than QM ones), and the calculated integral cross section and product distributions are in reasonable agreement with the experiment. The reaction occurs through an abstraction mechanism, following both a direct and an indirect mechanism. The quasiclassical trajectory calculations show the participation of a short-lived collision complex in the microscopic reaction mechanism. Finally, QCT differential cross sections of Cl+CH(4)-->HCl (nu(')=0 and 1)+CH(3) oscillate versus E(col), whereas experimentally this only occurs for HCl (nu(')=1). This theoretical result and other oscillating properties found here could, however, be related to the existence of a Feshbach resonance for the production of HCl (nu(')=1), as suggested by experimentalists.
利用基于从头算的准三原子表面，对上述反应进行了量子力学（QM）和准经典轨迹（QCT）研究。概率和积分截面相对于碰撞能量E(col)呈现出一些明显的峰值，我们将其归因于过渡态的费什巴赫共振，其中轻的H原子在重的Cl和CH(3)基团之间振荡。对于基态反应物，反应活性本质上源于量子（QCT可观测量和振荡比QM的小，或小得多），并且计算得到的积分截面和产物分布与实验结果合理吻合。该反应通过提取机制发生，遵循直接和间接机制。准经典轨迹计算表明，一个短寿命的碰撞复合物参与了微观反应机制。最后，Cl+CH(4)-->HCl（ν'=0和1）+CH(3)的QCT微分截面随E(col)振荡，而实验上仅HCl（ν'=1）出现这种情况。然而，正如实验人员所暗示的，这里发现的这一理论结果和其他振荡特性可能与产生HCl（ν'=1）的费什巴赫共振的存在有关。
