Unexpected angular distribution of the δ-electron emission in 1.4 MeV u^-1U³³⁺-rare-gas collisions

Abstract

Doubly differential delta -electron emission cross sections Delta 2 sigma (Ee, theta e)/ Delta Ee Delta Omega e have been measured as a function of the electron energy Ee and the electron emission angle theta e for the collision systems 1.4 MeV u-1 U33+ on neon and argon. The angular distributions of the emission cross sections show a maximum at theta e approximately=60', in agreement with parameter-free n-body classical trajectory Monte Carlo (n-CTMC) calculations. The cross sections show an extreme anisotropy between forward and backward emission compared with those of light-ion data. The cross sections decrease exponentially for theta e90'. The n-CTMC calculations indicate that the large projectile Coulomb force highly polarises the target-atom electrons in the two-centre field.