Departamento de Química Módulo 13, Universidad Autónoma de Madrid, 28049 Madrid, Spain.
J Chem Phys. 2012 Aug 14;137(6):064707. doi: 10.1063/1.4742907.
We have studied survival and rotational excitation probabilities of H(2)(v(i) = 1, J(i) = 1) and D(2)(v(i) = 1, J(i) = 2) upon scattering from Cu(111) using six-dimensional (6D) adiabatic (quantum and quasi-classical) and non-adiabatic (quasi-classical) dynamics. Non-adiabatic dynamics, based on a friction model, has been used to analyze the role of electron-hole pair excitations. Comparison between adiabatic and non-adiabatic calculations reveals a smaller influence of non-adiabatic effects on the energy dependence of the vibrational deexcitation mechanism than previously suggested by low-dimensional dynamics calculations. Specifically, we show that 6D adiabatic dynamics can account for the increase of vibrational deexcitation as a function of the incidence energy, as well as for the isotope effect observed experimentally in the energy dependence for H(2)(D(2))/Cu(100). Furthermore, a detailed analysis, based on classical trajectories, reveals that in trajectories leading to vibrational deexcitation, the minimum classical turning point is close to the top site, reflecting the multidimensionally of this mechanism. On this site, the reaction path curvature favors vibrational inelastic scattering. Finally, we show that the probability for a molecule to get close to the top site is higher for H(2) than for D(2), which explains the isotope effect found experimentally.
我们使用六维（6D）绝热（量子和准经典）和非绝热（准经典）动力学研究了 H(2)(v(i) = 1, J(i) = 1)和 D(2)(v(i) = 1, J(i) = 2)在散射到 Cu(111)时的生存和旋转激发概率。基于摩擦模型的非绝热动力学已被用于分析电子-空穴对激发的作用。与非绝热计算的比较表明，非绝热效应对振动去激发机制的能量依赖性的影响小于先前基于低维动力学计算所提出的影响。具体来说，我们表明 6D 绝热动力学可以解释振动去激发随着入射能量的增加而增加的现象，以及在 H(2)(D(2))/Cu(100)的能量依赖性中实验观察到的同位素效应。此外，基于经典轨迹的详细分析表明，在导致振动去激发的轨迹中，最小经典转折点接近顶位，反映了这种机制的多维性。在这个位点上，反应路径曲率有利于振动非弹性散射。最后，我们表明，分子接近顶位的概率对于 H(2)高于 D(2)，这解释了实验中发现的同位素效应。
