Institute for Physical Chemistry, University of Göttingen, Tammannstrasse 6, D-37077 Göttingen, Germany.
J Chem Phys. 2012 Jun 7;136(21):214309. doi: 10.1063/1.4717706.
The dissociation/recombination reaction CH(4) (+M) ⇔ CH(3) + H (+M) is modeled by statistical unimolecular rate theory completely based on dynamical information using ab initio potentials. The results are compared with experimental data. Minor discrepancies are removed by fine-tuning theoretical energy transfer data. The treatment accounts for transitional mode dynamics, adequate centrifugal barriers, anharmonicity of vibrational densities of states, weak collision and other effects, thus being "complete" from a theoretical point of view. Equilibrium constants between 300 and 5000 K are expressed as K(c) = k(rec)/k(dis) = exp(52,044 K/T) [10(-24.65) (T/300 K)(-1.76) + 10(-26.38) (T/300 K)(0.67)] cm(3) molecule(-1), high pressure recombination rate constants between 130 and 3000 K as k(rec,∞) = 3.34 × 10(-10) (T/300 K)(0.186) exp(-T/25,200 K) cm(3) molecule(-1) s(-1). Low pressure recombination rate constants for M = Ar are represented by k(rec,0) = [Ar] 10(-26.19) exp[-(T/21.22 K)(0.5)] cm(6) molecule(-2) s(-1), for M = N(2) by k(rec,0) = [N(2)] 10(-26.04) exp[-(T/21.91 K)(0.5)] cm(6) molecule(-2) s(-1) between 100 and 5000 K. Weak collision falloff curves are approximated by asymmetric broadening factors [J. Troe and V. G. Ushakov, J. Chem. Phys. 135, 054304 (2011)] with center broadening factors of F(c) ≈ 0.262 + (T - 2950 K)/6100 K for M = Ar. Expressions for other bath gases can also be obtained.
甲烷（CH4）（+M）⇔ 甲基（CH3）+ 氢（H）（+M）的离解/复合反应通过基于动力学信息的统计单分子速率理论进行建模，完全使用从头算势能。结果与实验数据进行了比较。通过微调理论能量转移数据消除了较小的差异。该处理方法考虑了过渡模式动力学、适当的离心势垒、振动态密度的非谐性、弱碰撞和其他效应，因此从理论角度来看是“完整的”。300 至 5000 K 之间的平衡常数表示为 K(c) = k(rec)/k(dis) = exp(52044 K/T) [10(-24.65) (T/300 K)(-1.76) + 10(-26.38) (T/300 K)(0.67)] cm(3) molecule(-1)，130 至 3000 K 之间的高压复合速率常数表示为 k(rec,∞) = 3.34 × 10(-10) (T/300 K)(0.186) exp(-T/25200 K) cm(3) molecule(-1) s(-1)。M = Ar 的低压复合速率常数表示为 k(rec,0) = [Ar] 10(-26.19) exp[-(T/21.22 K)(0.5)] cm(6) molecule(-2) s(-1)，M = N(2) 的速率常数表示为 k(rec,0) = [N(2)] 10(-26.04) exp[-(T/21.91 K)(0.5)] cm(6) molecule(-2) s(-1)，在 100 至 5000 K 之间。弱碰撞下降曲线通过不对称展宽因子[J. Troe 和 V. G. Ushakov，J. Chem. Phys. 135，054304（2011）]进行近似，对于 M = Ar，中心展宽因子 F(c)≈0.262+(T-2950 K)/6100 K。其他浴气体的表达式也可以得到。
