On the role of dipole transitions in the semiclassical approximation for K-shell ionisation

The role of the dipole-transition amplitude in the inner-shell ionisation of atoms by light ions is discussed within the framework of the semiclassical approximation. Analytical expressions for the projectile path factors for a hyperbolic projectile path are reported. The recoil of the target nucleus during the collision is taken into account by an extra non-inertial term in the electronic Hamiltonian, both for a relativistic and a non-relativistic electron description. The recoil correction strongly modifies the dipole amplitude at small impact parameters. The effects of binding and symmetrisation are also briefly discussed. Numerical results are reported for calculations of K-shell ionisation. (author)