Influence of ionised electrons on heavy nuclei angular differential scattering cross sections

Abstract

Abstract. For the collision systems 1.4MeVu- ' U3'+ and 5.9 MeVu- ' U65+ on Ne, transverse (with respect to the beam axis) momentum distributions of recoiling target atoms have been measured applying a time-of-flight technique. In the case of isotropic electron emission, the transverse momenta of the recoil ion pRL and the projectile ppl after the collision are identical. This allows the transformation of measured pRl distributions into projectile related differential scattering cross sections du/d8. Using such an analysis, we have measured differential cross sections in the scattering angle regime of 1 x r a d s 8 G 4 x rad. The shape, as well as the absolute magnitude of the derived experimental d a / d 8 is in reasonable agreement with Rutherford differential cross sections at large 8 using a projectile nuclear charge of 2, = qp and a target nuclear charge of Z, = 5. For 8 6 1 x rad, n-body classical trajectory Monte Carlo (nCTMC) calculations predict that the balance between pRl and ppI is strongly influenced by the momenta of anisotropi-cally emitted ionised electrons. From the comparison between the derived experimental cross sections d a / d 8 with the theoretical values, as well as from the agreement between experimental and theoretical transverse recoil-ion momentum distributions, we conclude that the momenta of the ejected electrons have a considerable influence on the scattering dynamics of the heavy nuclei. Furthermore, the calculations indicate that the projectile is scattered to negative angles at impact parameters of b 3 3a0 due to anisotropic electron emission and strong polarisation of the target electron cloud by the Coulomb potential of the projectile. The possibility of rainbow scattering at 8 = 1 x rad is predicted. 1.