Differential cross section measurements for elastic scattering of electrons by highly charged argon ions

Elastic scattering of electrons by highly charged ions, in particular the measurements of differential cross sections, is the focus of the present research. By using a 150 degrees crossed beam method, we have successfully measured the angular distributions of electrons elastically scattered from Ar7+ and Ar8+ ions over a wide angular range, employing a novel toroidal electron energy analyser, which is capable of simultaneous determination of the angle and the energy of the scattered electrons over a wide range. Relative differential cross sections for the e + Ar7+ system have been derived by employing results of e + Ar8+, which can be treated as pure Rutherford scattering, as a calibration for the detection efficiency over the angular range. In the angular range studied, between 34 degrees-85 degrees, experimental data of the e + Ar7+ system agree with the Rutherford classical cross sections fairly well, indicating that the Coulombic interaction dominates over this angular range, at a collision energy of 100 eV. Some small deviations from the Rutherford cross sections are considered to be due to the influences of the ionic structure to the scattering cross sections.