Abstract
Spin exchange cross sections have been calculated for hydrogen atoms with energy in the keV range incident on hydrogen or alkali-atom targets. The cross sections generally decrease with increasing energy, but also show oscillations as a function of the energy. For a hydrogen atom with an energy of 5 keV incident on a Na atom target, the total spin exchange cross sections is 1.2*10-15 cm2. The effect of spin exchange collisions on an optically pumped polarised H- ion source is analysed.