Close-Coupling Technique for Chemical Exchange Reaction of the Type A+BC→AB+C. H+H2→H2+H

Abstract

A new close‐coupling technique for rearrangement collisions of the form A+BC→AB+C is presented. The general theory is developed for collinear electronically adiabatic encounters. A central feature of the technique is the expression of the scattering wavefunction as a sum of two terms expressed in two symmetric coordinate systems. The first term is expressed in coordinates $R_{\mathrm{AC}}$ and $R_{\mathrm{BC}}$ appropriate to the arrangement A+BC prior to reaction and the second term in coordinates $R_{\mathrm{AC}}$ and $R_{\mathrm{AB}}$ appropriate to the arrangement AB+C after reaction. Coupled equations in the single variable $R_{\mathrm{AC}}$ are obtained and integrated numerically by an initial‐value technique to obtain accurate transition and reaction probabilities. The theory is applied to the exchange reaction H+H₂→H₂+H using the Porter–Karplus potential energy surface. Although the results cannot be compared directly with those of previous accurate quantal calculations, they are internally consistent and exhibit trends qualitatively similar to those of the previous calculations.