A Calculation of the Rates of the Ortho-Para Conversions and Isotope Exchanges in Hydrogen

Abstract

The rates of the various elementary reactions of the type H+H2→H2+H, involving ortho‐para conversions or isotope exchanges, have been calculated by the absolute reaction rate theory, using new fundamental quantum‐mechanical data for the shape of the H3energy surface, but estimating the activation energy to fit experimental results. The transition complex is linear and symmetric, in contrast with the asymmetric complex of the semiempirical surface, resulting in some qualitative, as well as quantitative, differences in the calculation. The tunnel effect correction is computed exactly, on the assumption that the potential barrier is of the Eckart type. The disparity between the experimental results obtained by different authors and the probable inaccuracies in their data make it very difficult to assess the accuracy of the calculated rate constants.