Electron capture to continuum in collisions of bare projectiles with Ne targets

Abstract. We have investigated the cusp resulting from electron capture to the continuum of 1.25-5 MeV m u- ' fully stripped hydrogen and oxygen as a function of the collision energy and the detector angular resolution B o. It is revealed that the characteristic cusp shape parameters depend strongly on the experimental resolution. Our experimental data are "pared with the second-order Born theory and the impulse approximation. Both theories mnhrm the 8, dependence of the shape parameters and gjve a reasonable descrip-lion of the cusp asymmetry. However, theory tends to overestimate the absolute cross sections, in particular in the case of oxygen. 1

Competing processes for electron capture to continuum in relativistic ion-atom collisions

The relative importance of the two mechanisms for the capture of a target electron by a fast, heavy projectile, radiative ionization (RI) and Coulomb capture to continuum (ECC), is studied in the vicinity of the forward peak. For both processes a consistent relativistic description, based on the impulse approximation, is provided. It is found that the differential cross-sections scale with the projectile charge and exhibit a common velocity dependence. As a result, RI starts to dominate over ECC near the same impact energy (~11 MeV/amu) for arbitrary bare projectiles colliding with hydrogen. For electrons from the inner shells of heavier targets this energy increases, however, which is confirmed by a coincidence experiment on 90 MeV/amu U88+ + N2

Strong potential second Born theory for low-energy electron emission in asymmetric collisions

The ejection of low-energy target electrons by heavy projectiles is calculated in a second Born approximation, allowing for propagation of the electrons in the strong projectile field. For neutral projectile impact this theory provides a satisfactory description of the collision process down to quite low impact velocities. This is shown by comparing the theory with experimental electron spectra from 0.1 MeV/amu Ne0 on He. However, when the projectile is charged the influence of its potential on the electronic final state may only be neglected for ejection of very low-energy electrons into the backward direction