ECC cusp and Coulomb boundary conditions

A wavefunction possessing the correct asymptotic behaviour in the region of configuration space where two particles are only slightly separated and a third particle is located far away, is suggested. This function cannot be represented as a product of independent two-particle distortion functions and in the limiting cases it passes into the continuum-distorted-wave function and the asymptotic wavefunction of Kunikeev and Senashenko. The latter function is used to investigate the double-differential cross sections (DDCS) for ionization of an atom by ion impact. The amplitude and the DDCS for the ionization process is developed. As an application of the theory, the DDCS as a function of the ejected-electron energy for ejection angle in the , collisions are calculated. The present results are compared with calculations performed with the continuum-distorted-wave-eikonal-initial-state and the impulse-approximation models and with the available experimental data. Good experimental agreement is obtained. It is found that the main contribution to the electron yield on the high- and low-energy wing of the electron capture to the continuum peak give the waves that are, and are not, rescattered by projectile ion respectively.