Investigation of the reaction X2 + X → X + X2 for X=H, D using the R-matrix theory

For the reaction considered, exact transition probabilities have been calculated on a Wall-Porter potential surface using the R-matrix theory of Wigner and Eisenbud. Similarly as for X=H, the transition probability shows a characteristic dip which is shown to correspond to a complex state. Reaction rates together with their mass dependence are calculated from the transition probabilities and compared with rates obtained from the theories of Eyring and of Eu and Ross. While the former theory yields the correct isotopic effects, the latter is shown to result in incorrect values. (author)