Effect of the Total Angular Momentum on the Dynamics of the H₂ + H₂ System

Abstract

Extended full-dimensional quasiclassical trajectory calculations have been performed for the H(a)H(b) (v(ab) = 10, 11, 12, 13, 14, j(ab) = 0) + H(c)H(d) (v(cd) = 0, j(cd) = 0) collisions at values of the translational energy ranging from threshold to 1.5 eV and values of the total angular momentum quantum number J varying from zero to very large ones. Collision-induced dissociation, four-center exchange reaction, and single exchange process probabilities have been calculated. Full-dimensional classical calculations were found to reproduce well the corresponding (J = 0) quantum results, including the thresholds. In contrast, the agreement of full-dimensional classical calculations with the corresponding both quantum and classical reduced dimensionality ones was found to be poor. The effect of varying J on the efficiency of the various processes has also been investigated. Four-center reactions were found to be favored by low values of J, whereas dissociation processes were found to be favored by higher values of J, as expected from the fact that energy exchange takes place at longer range than mass exchange. To evaluate to what extent the J = 0 full-dimensional calculations represent the unconstrained dynamics of the system, J-shift model classical results were compared with the all-J ones. Product vibrational distributions for both partially dissociative and exchange processes were also found to depend significantly on the value of J.

Fully converged integral cross sections of collision induced dissociation, four-center, and single exchange reactions, and accuracy of the centrifugal sudden approximation in H2 + D2 reaction

“…38 We found that the necessary J max increases with both collision and vibrational energy for all the three processes. The CID process occurs in a wide range of J values and shows a long tail.…”

“…These behaviors can be explained by a hard sphere model. As indicated by Garcia et al, 38 the narrow window of J in the 4C process can be attributed to a locking radius, depending on the bond length at which the exchange occurs. In the CID process, the larger range of J can be associated with the radius of optimum vibration-translation energy exchange.…”

“…38 To further attest their conclusions in the QM frame, we here also study the efficiency of varying J on the various processes in H 2 + D 2 . Figures 4-6 present the 6D CC CID, 4C, and SE probabilities for the H 2 (v 1 = 10, 11, j 1 = 0) + D 2 (v 2 = 0, j 2 = 0) reaction at several selected collision energies as a function of J.…”

“…Therefore, most theoretical dynamics studies have been performed using reduced dimensional or fulldimensional classical or quasi-classical trajectories (QCT) (Refs. [30][31][32][33][34][35][36][37][38] and reduced dimensional quantum mechanical (QM) methods. 29,[39][40][41][42][43][44] Lu et al 45 carried out the first accurate full-dimensional QM calculations of the H 2 + H 2 reaction using the time-dependent wave packet method.…”

A high‐level ab initio study of the N2 + N2 reaction channel

“…This is the case for the H 2 ‐H 2 and N 2 ‐N 2 systems for which in the last three decades a certain number of theoretical and experimental investigations have been carried out . For example, a reliable and versatile potential energy surface (PES) developed for the (H 2 ) 2 system was used by some of us for extended dynamical calculations …”