Dynamics Study of the H + ArO₂ Multichannel Reaction

Abstract

Trajectory calculations have been carried out for the title reaction over the range of translational energies 0.25 e E tr /kcal mol-1 e 131.4. We present reactive cross sections for formation of stable HO 2 for translational energies up to 8.0 kcal mol-1 , while for O 2 formation the reported cross sections extend over the whole range of translational energies. The former cross sections are shown to decrease with increasing translational energy, while the latter cross sections show a slight increase leading to a broad maximum and finally approach zero at high energies. Similarly, the formation of OH products has been investigated in detail and compared with the corresponding process in the absence of argon. Formation and dissociation of energized HO 2 * complexes have also been analyzed and the decay rates rationalized by means of a simple two-step kinetic mechanism.

What are the Implications of Nonequilibrium in the O+OH and O+HO2 Reactions?

“…Although HO * 2 could be taken a priori as dissociative to give H + O 2 or O + OH, this has not been done as the true outcome may depend on whether there is a collision before the unimolecular dissociation process occurs. Thus, we chose to initiate the trajectories with the HO 2 vibrational excitations given by Equation (30). Once the vibrational energy is defined, the standard fixed normal-mode sampling procedure [43] is used to distribute it by the three vibrational normal modes of HO 2 .…”

“…Note that the atomic hydrogen produced in reaction (6) reacts with O 2 in the presence of a third body [29,30] to yield HO 2 [31] or, eventually, with O 3 to form OH(v) and O 2 . [32] However, it is unlikely that a reduction [33] in k 7 or the ratio k 7 /k 6 would decrease [OH] in the mesosphere and, simultaneously, increase [OH] at lower altitudes.…”

Dynamics Study of the Reaction Ar + HCN → Ar + H + CN

“…Although in this case the configurational definition of the complex versus dissociated molecule may present some ambiguity, the subsequent dynamics study of its unimolecular dissociation can provide additional valuable information. 18,38 …”

“…The dynamics of the HCN* complexes with energy above dissociation can be used to estimate the microcanonical or canonical unimolecular decay rate HCN* f H + CN. Following previous work, 18 a brief discussion of their dynamics will be attempted. Thus, after the HCN* complexes have been formed, the trajectories were allowed to continue until dissociation occurs or a limiting time of 60 ps has been achieved.…”

Trajectory Dynamics Study of the Ar + CH4 Dissociation Reaction at High Temperatures: the Importance of Zero-Point-Energy Effects

“…The reactive cross sections have been calculated by running trajectories with an extensively adapted version 44,51,52 of the MERCURY program, 53 which allows for the definition of all possible reactive channels. 44 This has been further modified to incorporate the proper selection of initial conditions for the present work that we describe as follows.…”