Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published December 1, 1976 | Published
Journal Article Open

Quantum mechanical reactive scattering for planar atom plus H_2 diatom systems. II. Accurate cross sections for H+H_2


The results of an accurate quantum mechanical treatment of the planar H+H_2 exchange reaction on a realistic potential energy surface are presented. Full vibration–rotation convergence was achieved in the calculations, and this, together with a large number of auxiliary convergence and invariance tests, indicates that the cross sections are accurate to 5% or better. The reactive differential cross sections are always backward peaked over the range of total energies from 0.3 to 0.65 eV. Nonreactive j=0 to j′=2 cross sections are backward peaked at low energy (0.4 eV) shifting to sidewards peaking for E≳0.5 eV. Quantum symmetry interference oscillations are very significant in the j=0 to j′=2 para‐to‐para cross sections for E≥0.6 eV. Reactive integral cross sections show two distinct kinds of energy dependence. At low energy (<0.5 eV), barrier tunneling gives them a largely exponential energy dependence while above 0.5 eV (the effective threshold energy) the cross sections vary nearly linearly. Comparison of collinear and coplanar transition probabilities indicates similar 1D and 2D energy dependence but with a shift in energy from 1D to 2D due to bending motions in the transition state. An analysis of rotational distributions indicates surprisingly good correspondence with temperaturelike distributions. The results of a one‐vibration‐approximation calculation are examined, and errors of as much as three orders of magnitude are found at some energies. Shapes of angular distributions are, however, accurately predicted by this approximate method. Additional analyses include comparisons with previous distorted wave and coupled‐channel results, and calculations of thermal rate constants.

Additional Information

© 1976 American Institute of Physics. Received 22 December 1975. Online Publication Date: 28 August 2008. Special thanks are due to Professor J. D. Roberts, who as chairman of the Division of Chemistry and Chemical Engineering at Caltech during the crucial stages of this research mustered the financial resources and offered the encouragement which were central to its successful completion. We thank Ambassador College for generous use of their computational facilities. We also thank Professor Donald G. Truhlar for useful comments. Work supported in part by the United States Air Force Office of Scientific Research (Grant No. AFOSR-73-2539). Work performed in partial fulfillment of the requirement for the Ph. D. degree in Chemistry at the California Institute of Technology. Contribution No. 5249.

Attached Files

Published - SCHAjcp76a.pdf


Files (1.4 MB)
Name Size Download all
1.4 MB Preview Download

Additional details

August 19, 2023
August 19, 2023