Atomic processes are important in determining the particle-antiparticle annihilation rates in the matter-antimatter interaction. Consideration of these processes is given for a hydrogen-antihydrogen mixture. The atomic effects considered are the effect of the Coulomb field on the direct annihilations, radiative capture, and rearrangement collisions. Radiative capture and rearrangement reactions lead to particle-antiparticle bound states from which annihilation proceeds. The rearrangement cross sections are considerably greater than the direct-annihilation cross sections and therefore lead to a large increase in the total annihilation rates over a wide range of kinetic energies. The lifetimes of two types of hydrogen-antihydrogen mixtures are calculated and are found to differ significantly from the results obtained by others.

• Received 23 January 1970

DOI:https://doi.org/10.1103/PhysRevD.2.1389