Ellerbrock Roman, Mantheuwe Uwe
Theoretische Chemie, Fakultät für Chemie, Universität Bielefeld, Universitätsstr. 25, D-33615 Bielefeld, Germany.
Faraday Discuss. 2018 Dec 13;212(0):217-235. doi: 10.1039/c8fd00081f.
Natural reaction channels are defined by the singular value decomposition of the S-matrix and can be interpreted as pathways through the transition state of the reaction. Here, the reaction probabilities and asymptotic state distributions associated with the natural reaction channels of the H + CHD3 → H2 + CD3 reactions are presented. The analysis is based on accurate quantum dynamics data obtained by full-dimensional (multi-layer) multi-configurational time-dependent Hartree (MCTDH) calculations using the quantum transition state framework and a high-level ab initio potential energy surface. The reaction starting from several different initial ro-vibrational states is investigated. The results provide interesting insights into symmetry-related differences between the mode-selective chemistry of CH4 and CHD3. The presence of localized vibrational modes in CHD3 is found to limit the loss of memory effect seen in the H + CH4 → H2 + CH3 reaction and to give rise to spectator behavior of the selected modes. Furthermore, the recently found reactivity borrowing effect, which results from a Fermi resonance-type state mixing of the triple umbrella excited and single C-H-stretch excited states of CHD3, is investigated. Here, the natural reaction channel analysis provides detailed information on the resonant energy transfer in the entrance channel of the reaction and the correlation between the asymptotic states of the reactants and the vibrational states of the activated complex.
自然反应通道由S矩阵的奇异值分解定义，可解释为通过反应过渡态的路径。本文给出了与H + CHD3 → H2 + CD3反应的自然反应通道相关的反应概率和渐近态分布。分析基于通过全维（多层）多组态含时Hartree（MCTDH）计算获得的精确量子动力学数据，计算使用了量子过渡态框架和高精度的从头算势能面。研究了从几种不同初始转动 - 振动态开始的反应。结果为CH4和CHD3的模式选择性化学之间与对称性相关的差异提供了有趣的见解。发现CHD3中局域振动模式的存在限制了在H + CH4 → H2 + CH3反应中观察到的记忆效应的损失，并导致所选模式的旁观行为。此外，还研究了最近发现的反应性借用效应，该效应源于CHD3的三重伞激发态和单C - H拉伸激发态之间的费米共振型态混合。在此，自然反应通道分析提供了关于反应入口通道中共振能量转移以及反应物渐近态与活化络合物振动态之间相关性的详细信息。
