Simple DWBA (''Franck--Condon'') treatment of H-atom transfers between two heavy particles

A simple DWBA (Franck--Condon) method for calculating the probability of transferring a light particle between two heavy ones in a collinear collision at energies below and around the reaction threshold is presented. The region is the important one for the thermal reaction rates. The method is tested for two different model LEPS surfaces for H-atom transfer with moderately high barriers. The results are in good agreement with those of accurate multichannel calculations.The transition probability is calculated as an overlap integral over the reactants' and products' wave functions and the interaction potential. The reactants' and products' wave functions are calculated from their respective distortion potentials as one-term adiabatically separable approximations. Both the distortion potentials and the interaction potentials are extracted straightforwardly from the LEPS surface. The novel feature of the approach is that for the first time accurate results for the absolute values of the reaction probability are obtained from a simple overlap of single-channel approximate wave functions obtained directly from the respective parts of the potential energy surface for the reaction