A Quasiclassical Trajectory Study of Product Energy and Angular Distributions in OH + H2 (D2)

Abstract

We present a quasiclassical trajectory study of OH + H2 -H2O + H and its D2 counterpart using the Schatz-Elgersma semiempirical potential surface. Emphasis in the work has been on using an accurate determination of the H2O vibrational actions to calculate product vibrational state distributions. Other aspects of the product energy and angular distributions have also been studied so as to make comparisons with recent molecular beam and laser experiments and with other calculations. The OH + H2 results generally confirm earlier calculations by Schatz and Elgersma, but the vibrational distributions are somewhat different, indicating that the earlier perturbation theory-based calculations were not completely converged. The calculated OH + Hz(D2) integral cross sections are in good agreement at energies close to the reactive threshold with quantum calculations due to Nyman and Clary. Comparisons with recent measurements by Koppe et al. indicate good agreement for OH + Dz but not as good for OH + H2. The OH + D2 product angular distributions are in good agreement with measurements by Casavecchia and co-workers, but the fraction of energy in translation is significantly higher (0.45 vs 0.32). Nyman and Clary's fraction of energy in translation for the same potential energy surface is higher still (0.71). Their calculation leaves out HOD rotation, which may explain thedifferences between the two theoretical estimates. The difference between theory and experiment is probably due to inaccurate energy release behavior in the potential surface, with too little energy going to product vibration.

Dynamics of H2 Eley-Rideal abstraction from W(110): Sensitivity to the representation of the molecule-surface potential

“…As apparent from Fig. 9, QCT results, computed within the standard binning method, 91 are in remarkable agreement with experiments up to v = 5 vibrational state for the FPLEPS PES. The choice of the binning procedure for vibrational action 92,93 has negligible influence on vibrational state distribution.…”

A theoretical study of the NH+NO reaction

“…31 The code has extensive capabilities for analyzing the reagent and product vibrational states by determining vibrational action variables, as has recently been reviewed. 31 As a result, it is possible for us to calculate cross sections from selected vibration/rotation states of the reagents NHϩNO to all states of OHϩN 2 and HϩN 2 O that are significantly populated.…”

“…31 The code has extensive capabilities for analyzing the reagent and product vibrational states by determining vibrational action variables, as has recently been reviewed. 31 As a result, it is possible for us to calculate cross sections from selected vibration/rotation states of the reagents NHϩNO to all states of OHϩN 2 and HϩN 2 O that are significantly populated. In the present calculations we only present results for the ground states of the reagents, but we have also studied NHϩNO in their thermally ͑300 K͒ most probable rotational states, and we find that rotation has a negligible effect on reaction.…”

Quasiclassical Trajectory Studies of State-Resolved Bimolecular Reactions: Vibrational Distributions in Triatomic Products

“…There have been several theoretical studies of product vibrational distributions for (R. 1) based on approximate q~a n t u m~*~, '~ or semiclassical9 calculations. Detailed comparisons are in ref 25, and for many aspects of the vibrational distributions, our results are in approximate agreement with results from Clary,4 Bowman,5 and Billing.9 One aspect that does not agree is the ratio of (100) and (001) cross sections in OH + H;!. We find that these cross sections are generally comparable in magnitude, with a ratio that oscillates with energy, while Wang and Bowmansb and Billing9 find that (100) is consistently larger, and Szichman et aZ.1° find that (001) is larger.…”