Born鈥揙ppenheimer and Renner鈥揟eller Quantum Dynamics of CH(X2螤) + D(2S) Reactions on Three CHD Potential Surfaces

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• 作者：Pablo Gamallo ; Sinan Akpinar ; Paolo Defazio ; Carlo Petrongolo
• 刊名：Journal of Physical Chemistry A
• 出版年：2015
• 出版时间：November 19, 2015
• 年：2015
• 卷：119
• 期：46
• 页码：11254-11264
• 全文大小：631K
• ISSN：1520-5215

文摘

The quantum dynamics of three CH(X²螤) + D(²S) reactions is studied by means of the coupled-channel time-dependent real-wavepacket (WP) and flux methods at collision energy E_col 鈮?0.6 eV and on three potential energy surfaces (PESs): the Born鈥揙ppenheimer (BO) ground PES X虄³A鈥?and the excited ones 茫¹A鈥?and b虄¹A鈥? coupled by nonadiabatic (NA) Renner鈥揟eller (RT) effects. This three-state model is suitable for obtaining initial-state-resolved observables, is based on a complete analysis of the correlation diagram of the lowest electronic states of the CHD intermediate and of their NA interactions, and neglects the smaller coupling effects due to the asymptotic electronic angular momenta that become important in state-to-state dynamics. WPs are propagated on each PES at total angular momentum values J 鈮?70, with CH in the two lowest vibrational states v₀ and in the ground rotational state j₀ = 1. Reaction probabilities are obtained for three possible final products (f): (dP) CH decay and C(³P) + HD(X¹危⁺) formation that occurs on the uncoupled ground PES, (dD) CH decay and C(¹D) + HD(X¹危⁺) formation that depends on the RT-coupled singlet species, and (ex) exchange to CD(X²螤) + H(²S) available adiabatically from the X虄³A鈥?PES and nonadiabatically from 茫¹A鈥?and b虄¹A鈥? Observable cross sections 蟽_f,v0j0 and rate constants k_f,v0j0 in the temperature range T = 100鈥?000 K are obtained for (dP), (dD), and (ex) channels. Comparing BO with RT probabilities, we show that NA effects are important at high J values for the (ex) channel at v₀ = 1. Real time mechanisms on the three PESs show that RT couplings are opened after some time and clearly point out the formation of the product channels. Both cross sections and rate constants present the same sequence, for example 蟽_ex,11 > 蟽_dP,01 鈭?蟽_ex,01 > 蟽_dP,11 鈮?蟽_dD,11 鈮?蟽_dD,01, and the CH vibrational excitation enhances the total removal CH+D reactivity by a factor of 鈭?.7, mainly due to the increase of the (ex) channel contribution from 鈭?7% at v₀ = 0 to 鈭?6% at v₀ = 1. This fact implies a considerable vibrational enhancement of combustion processes at high temperature. In agreement with the probability results, the 茫¹A鈥?b虄¹A鈥?RT coupling increases both 蟽_ex,11 and k_ex,11 up to 鈭?0%. Moreover, including the three PESs in the dynamics simulation of CH+D increase by far the (ex)/(dP) branching ratio with respect to the CH + H鈥?reaction. Thus, at room temperature, k_dP,01 changes from 10.8 脳 10^鈥?1 to 3.4 脳 10^鈥?1 cm³ s^鈥? substituting H atom by D.