Inelastic Collisions between Heavy Particles III: Excitation of Helium Atoms in Fast Encounters with Hydrogen Atoms, Protons and Positive Helium Ions

Born's approximation is used to calculate the cross sections for the processes H (1s) + He (1s 2 ) → H(2s, 2p, 3s, 3p, 3d or C) + He (1s2p 1 P) where C represents the continuum. It is found that these double transition collisions are collectively much more effective at high impact energies than the simple single transition collision H (1s) + He(1s 2 ) → H (1s) + He (1s2p 1 P) which is also investigated. Born's approximation is further used to calculate the cross sections for the processes He + (1s) (or H + ) + He (1s 2 ) → He + (1s) (or H + ) + He (1s2p 1 P) double transitions being here found to be unimportant.