Efficient quantum-classical method for computing thermal rate constant of recombination: Application to ozone formation

Abstract

Efficient method is proposed for computing thermal rate constant of recombination reaction that proceeds according to the energy transfer mechanism, when an energized molecule is formed from reactants first, and is stabilized later by collision with quencher. The mixed quantum-classical theory for the collisional energy transfer and the ro-vibrational energy flow [M. Ivanov and D. Babikov, J. Chem. Phys. 134, 144107 (2011)] is employed to treat the dynamics of molecule + quencher collision. Efficiency is achieved by sampling simultaneously (i) the thermal collision energy, (ii) the impact parameter, and (iii) the incident direction of quencher, as well as (iv) the rotational state of energized molecule. This approach is applied to calculate third-order rate constant of the recombination reaction that forms the (16)O(18)O(16)O isotopomer of ozone. Comparison of the predicted rate vs. experimental result is presented.

Ro-vibrational quenching of CO (v = 1) by He impact in a broad range of temperatures: A benchmark study using mixed quantum/classical inelastic scattering theory

“…38 This approach eliminates the problem of zero-point energy leakage, and also allows capturing other quantum mechanical phenomena, such as scattering resonances (including calculations of their lifetimes 41,42 ), quantization of vibrational states, their normal vs. local mode character, and finally, quantum symmetry. 43 The MQCT method [39][40][41][42] is expected to work well when the rotational quantum is small compared to thermal energy. This condition may not be fulfilled entirely for the lightest rotors only, such as methane or water (both contain H atoms), but it is satisfied well for majority of molecules, including heavy diatomics such as CO, O 2 , N 2 , etc.…”

Recent Advances in Development and Applications of the Mixed Quantum/Classical Theory for Inelastic Scattering

“…The largest body of Billing's work was dedicated to development and testing of this approach. Recently, we applied similar methods to describe stabilization of scattering resonances at the final step of the ozone forming reaction, in O3* + Ar collisions, looking at the isotope effects, [51][52][53] but also in the benchmark study of ro-vibrational quenching in CO(v = 1) + He. 54,55 However, our major focus has been on the second implementation of MQCT, in which all the internal degrees of freedom are treated quantum-mechanically (rotational and vibrational states on equal footing) and only the scattering is described classically.…”

Mixed quantum/classical calculations of total and differential elastic and rotationally inelastic scattering cross sections for light and heavy reduced masses in a broad range of collision energies

“…2,3 In recent years such methods have been revived and improved, [4][5][6] and applied to complicated problems, such as recombination reactions. [7][8][9] For description of rotationally inelastic scattering Billing proposed another version of MQCT, in which the rotational motion is treated quantum mechanically, and only the translational motion is treated classically. 2,3 He applied this theory to one system, He + H 2 , at two relatively high values of scattering energies: E = 0.1 and 0.9 eV.…”