Discussion of electron capture theories for ion-atom collisions at high energies

The authors consider different theories of charge exchange processes in ion-atom collisions at high energies for the H + -H system. Large discrepancies are found in the differential cross sections obtained from the various models. The validity of Dettmann's peaking approximation (1968, 1969) is analysed by comparison with exact values for the first- and second-order Oppenheimer-Brinkman-Kramers (OBK 1 and OBK 2) theories. It is also shown that for energies up to a few MeV the OBK 2 differential cross sections are higher than the corresponding OBK 1 ones. Total cross sections in the OBK 2 approximation are given.