Influence of collision energy on the dynamics of the reaction O(1D) + CH4(X1A1) → OH(X 2Π) + CH3(X 2A2″)

Abstract

We studied the effects of collision energy (ET) on the dynamics of the title reaction using the quasiclassical trajectory method on an analytical triatomic potential energy surface we had derived for this system. We compared the dependence of the scalar and two-vector properties of the reaction on ET with experimental data and obtained a quite good agreement. The results can be explained in terms of the coexistence of two microscopic reaction mechanisms: insertion and abstraction. The former mechanism is the most important one, although the contribution of the latter increases with ET.

Quantum dynamical study of the O(1D) + CH4 → CH3 + OH atmospheric reaction

“…This is particularly evident for E c = 0.5 eV and appears to be consistent with the existence of two main microscopic mechanisms found in QCT calculations. 4,24,36,37 Similar trends were obtained for the other rotational distributions, OH(v = 1-3, j ).…”

“…[4][5][6] The CH 3 OH reaction intermediate can be formed rather easily via insertion of O( 1 D) into a C-H bond of methane. 4,6,24,36,37 The particular importance of the CH 3 + OH channel (which has a kinematics nearly identical to reactants) is probably due to the fact that the other channels are less exoergic or present a barrier with respect to CH 3 OH.…”

How Active Is the Bend Excitation of Methane in the Reaction with O(3P)?

“…A classical barrier height lays around 13-14 kcal/mol (or 9-10 kcal/mol when the zero-point energy is included). Several dynamics investigations, using quasi-classical trajectories (QCT) 10,16 or reduced-dimensionality quantum models, [5][6][7][8]13,14 have been reported, and the calculated kinetic behaviors and product state distributions are generally in good agreement with experimental findings. 22 In addition, the modespecific reactivity has been under scrutiny using reduceddimensionality quantum scattering approaches.…”

“…In the other words, umbrella-mode excitation of CH 4 was partially preserved in the analogous nuclear motion of the CH 3 product, suggesting a spectator behavior of the CH 3 moiety in the reaction. 10 This view seems in keeping with a noninverted umbrella excitation of CH 3 products found experimentally 23 for the ground-state reagents. On the other hand, the concept of adiabaticity has its root on the relative time scales of nuclear motions.…”

“…1 Among those reactions, the abstraction reaction of O( 3 P) + CH 4 f OH + CH 3 is the simplest one for all saturated hydrocarbons, serving as the prototype for detailed investigations; as such, this reaction has attracted considerable interests, both experimental 2-4 and theoretical, [5][6][7][8][9][10][11][12][13][14][15][16][17][18] over the past decades. The reaction is slightly endothermic by 1.59 kcal/mol with a substantial barrier to reaction.…”