Pattern analysis of the impact‐parameter dependent trajectories for the H + H₂ exchange reaction at T = 3 and 300 K: A characteristic propensity for reactive versus nonreactive trajectories found in the time‐dependent interaction potential and a roaming‐like libration motion at cold temperature

Abstract

Pattern analysis of the impact‐parameter dependent trajectory for the H + H2 exchange reaction was performed at temperatures T = 3 and 300 K by employing the quasi‐classical trajectory calculation on a London‐Eyring‐Polanyi‐Sato surface. We find that (a) 0.66 fraction of reactive trajectories throughout b = 0.0 ~ 5.0 Å at T = 3 K, while only 0.33 at T = 300 K only for b = 0.0 ~ 1.5 Å and decreases soon to zero for b = 2.5 ~ 5.0 Å. (b) Ninety eight percent of the trajectories showed direct collision pattern at T = 300 K, while at T = 3 K, 72% for direct collision trajectories and 28% showed the intermediate H + H2 complex formation pattern. These results suggest that nonzero impact‐parameter trajectories play a role at T = 3 K to enhance reactivity due to long‐range attraction forces. Trajectory pattern analysis reveals a characteristic propensity rule between the amplitude of the time‐dependent interaction potential and the trajectory reactivity, thus we can judge if a trajectory is reactive or nonreactive. The analysis also proposes a roaming‐like libration motion at T = 3 K like in the interstellar clouds.

Concerted stereodynamics of chemical changes: The branching selectivity in the photodissociation of asymmetric‐top molecules, formic acid, and the cold reactivity of the H + H2 exchange reaction

“…To describe the H + H 2 interaction, we employed London‐Eyring‐Polanyi‐Sato potential energy surface and Morse function with the known corresponding experimental spectroscopic constants for the H 2 molecule [122–126]. About the computational details, you may refer to our original paper [119]. This trajectory pattern analysis provides sample data of at least 300 trajectories per impact‐parameter b , per temperature, as the total of 6600 trajectory calculations and a trajectory progresses with a time step of s = 0.1 fs .…”

“…Schematic picture for representing ideas of the trajectory pattern analysis employed in this trajectory computation. Reproduced from Reference 119 with permission from John Wiley and Sons.…”

“…The impact‐parameter b ranges from 0.0 to 5.0 Å with the 0.5 Å interval. Reproduced from Reference 119 with permission from John Wiley and Sons.…”

“…The interaction potential E ABC [kcal/mol] and its corresponding Lagrangian are shown in green and red, respectively. Reproduced from Reference 119 with permission from John Wiley and Sons.…”

“…Reproduced from Reference 119 with permission from John Wiley and Sons.To describe the H + H 2 interaction, we employed London-Eyring-Polanyi-Sato potential energy surface and Morse function with the known corresponding experimental spectroscopic constants for the H 2 molecule[122][123][124][125][126]. About the computational details, you may refer to our original paper[119]. This trajectory pattern analysis providesF I G U R E 1 4 An example of reactive trajectory resulting from the three-step direct collision trajectory pattern with the energy transfer to translation at b = 2.0 Å.…”