On the construction of perturbation integrals for the description of reactive molecular collisions

Abstract

We continue our investigation of the relative effectiveness of conventional and quasiadiabatic (QA) perturbation schemes in the determination of reactive transition probabilities. The simple problem of particle reflection and transmission at a one-dimensional potential barrier (loosely based on the minimum energy path interaction of the H+H2 system) is again adopted for our calculations. By examining the accumulation with reaction coordinate of exact and conventional perturbative probability integrals over a wide range of energies and for both low and high system masses (on a molecular scale), we have been able to account for our recent observations with regard to the high mass ineffectiveness of the conventional scheme. The effectiveness of a QA based scheme at high mass, also observed in our earlier work, is here give more substance by the development of a procedure for optimizing parameters of the (QA) representation. The procedure tempers maximization of the QA transmission (with respect to parameter variation) by also driving for a balance between its diabatic and nonadiabatic component contributions. Comparing for the optimized QA parameters and at a high system mass, exact and QA accumulating probability integrals, we find very good agreement.